Thomas Wright

 in T. WRIGHT (1857-1878) Monograph on the British Bossil Echinodermata of the Oolitic Formations

Vol.I - The Echinoidea, pages 44-50.

CIDARIS FLORIGEMMA, Phillips.  Pl. II, fig. 2 a, b, c, d, e, f ; Pl. VIII, fig. 4 a, b, c, d.

Test round, much inflated at the sides, and depressed at both poles, ambulacral areas narrow, elevated, and sinuous, with two marginal rows of granules set on basal eminences? and in the widest part of the area, two other rows of very small granules, without basal eminences, the middle rows disappear at both ends of the areas: inter-ambulacral areas wide, with two rows of primary tubercles, from six to seven in each column ; areolas rather oblong, and surrounded by a prominent elevated scrobicular circle of well-spaced-out granules, set on shield-like bases; miliary zone wide, concave, and filled with several rows of small granules; mouth opening small, peristome pentagonal; apical disc opening large and pentagonal; primary spines with large, thick, cylindrical stems, ornamented with longitudinal rows of prominent, forward-directed granules $ secondary spines short and spatulate, covered with fine longitudinal lines; tertiary spines small, conical, or oval shaped.

Dimensions.—a. Large specimen: Equatorial diameter, two inches and four tenths of an inch; height, one inch and seven twentieths of an inch.

b. Large specimen: Equatorial diameter, two inches and two tenths of an inch; height, one inch and four tenths of an inch.

c. Usual-sized specimen : Equatorial diameter, one inch and four tenths of an inch; height, one inch and four tenths of an inch.

Description.—This noble urchin was very abundant in the Corallian Seas of Europe, and its test and spines form characteristic fossils of this stage of the Jurassic group. Much confusion regarding this species has been caused by Goldfuss having figured, along with the test of Cidaris Blumenbachii Miinster, the spines of three or four other species of urchins, and especially in having erroneously described the spines of Cidaris florigemma as belonging to the test of Cidaris Blumenbachii.   I am indebted to my friend Mr. S. P. Woodward for having called my attention to this subject, as he has always maintained that Cidaris florigenima, Phil., was distinct from Cidaris Blumenbachii, Goldf. Having been fortunate in finding the slab, figured in PI. II, fig. 3 a, containing a small Cidaris florigemma with spines attached, I had direct evidence that the spines figured by Goldfuss as those of Cidaris Blumenbachii in reality belonged to the Wiltshire urchin. The next point to be ascertained was, whether the test figured by Goldfuss was different from the test of this species. A critical examination and comparison of good type speci­mens of Cidaris Blumenbachii, one in the collection of the British Museum, and another kindly sent me by Dr. Eraas, of Stuttgard, with the specimen figured in PI. II, fig. 2 b, e, has proved that they are very distinct from each other.

Plott, in 1677, figured the spines of this urchin under the name of Lapides Judaici. He says—" We find them here (Oxfordshire) of different sizes, from about two inches in length and an inch and a half in circuit, downwards to an inch and less in length and not much above half an inch round. Most of them have a pedicle from which they seem to have had their growth, and are ridged and channelled the whole length of the stone, the ridges being parted with small knots set in quincunx order. As to their texture, I find it to be very curious, made up of lamellae or little thin plates, not unlike the stone Selenites; only these are opaque, and the whole bulk of the stone indeed much different. The plates, as in the Selenites, seem to be made up of strings, which in most of them run three, but in some but two ways: according to the running of these strings the stones will easily cleave, but generally some one way rather than any other, which most commonly is agreeable to the helical running of the ridges of knots or furrows between them, yet always obliquely to the axis of the stone, as is perfectly shown, tab, vi, fig. 9, which represents the stone broken three several ways.^{" *}

Lhwydd, in 1690, figured spines of the same species from the Coral Rag of Oxford­shire. Parkinson, in his "Organic Remains of a Former World", gave a beautiful figure of the test (PI. I, fig. 9), which, it is but just to state, has been entirely overlooked, the references to his work having been made only to the figures of the spines (PI. IV, figs. 15, 17); the first good figure of the test of this species therefore is, in reality, that of Parkinson's. In the "Petrefacta Germaniae" Goldfuss gave good figures of the spines which he stated appertained to the test of Cidaris Blumenbachii; and subsequent palaeontologists, believing his statement, have nearly all followed his error. In the ^"Description des Echinodermes Fossiles de la Suisse" M. Agassiz has figured the spines of Cidaris florigemma with the test of Cidaris Blumenbachii; this is shown in the figure by the small-ness of the granules of the scrobicular circle, in the smallness of the tubercles, and the depth of the crenulations on the summits of the bosses, a group of characters which belong to Cidaris Bhtmenbachiii.   In the "Geology of Yorkshire", Professor John Phillips figured a test and spine of this species, under the name Cidaris florigemma, from a Wilt­shire specimen now in the Museum of the Yorkshire Philosophical Institution ; the correct­ness of the determination then made has been proved by the tedious investigation which was necessary to clear away the existing confusion relative to this species. M. Desor, in his ^"Synopsis des Echinides Fossiles", restricts the name Cidaris Blumenbachiii to the spines, ^"aculei non testa", figured by Goldfuss; but I cannot agree with my friend in this con­clusion, because Minister gave the name to the test, about which there can be no mistake. Goldfuss's error consisted in describing and figuring spines as belonging to this test which appertained to another species; therefore I say "testa non aculei³' in the synonym: as the test is the body of the animal, and the spines are merely appendages of the same, it follows that the name given by an author to a species must in every case relate to the major, and not to the minor part described. Minister's name, therefore, must still be given to the German form; which, as far as is at present known, has not yet been found in England. M. Desor observes: " J'ai ete fort longtemps dans Ie double sur les limites de cette espece, par la raison que les radicles et Ie test que Goldfuss a reunis, n'appartiennent pas au meme oursin. C'est tout recemment que la decouverte de quelques echantillons avec leurs radioles attaches au test, m'a permis de rectifier Ferreur dans laquelle j^etais tombe avec d'autres paleontologistes. Le test figure par Goldfuss n'a rien de commun avec les radioles qu'il lui attribue; il appartient a une autre espece decrite ulterieurement par M. Agassiz sous le nom de C. Parandieri. Or, comme les radioles sent bien plus abondants que les tests et qu'ils sont connus de tons les paleontologistes c'est a eux, et partant autest decrit ci-dessus, que je crois devoir conserver Ie nom primitif de Cidaris Blumenbachii. **

The test of Cidaris jlorigemma is round, and much inflated at the sides; it is mode­rately depressed at both poles, but is most so on the upper surface; the ambulacral areas are narrow, and nearly of a uniform breadth throughout; they are very sinuous and pro­minent, and are furnished with two rows of granules on the margins of the areas; between these, for about the length of two of the large tubercular plates, there are two rows of very small granules internal to the marginal ones (PI. II, fig. 2 g); the marginal granules are raised on small basal eminences, but the internal granules are not; the six or eight marginal pairs nearest the peristome are very much larger than those in the middle and upper parts of the areas: the poriferous zones are of moderate width; the pores forming a pair are separated from each other by a septum equal in width to the diameter of a pore (fig. 2 g) ; there are nineteen or twenty pairs of pores opposite each of the large equatorial tubercular plates; the zones are rather deep, from the prominence of the ambulacral areas in the middle, and that of the scrobicular circles external to them.

The inter-ambulacral areas are nearly five times the width of the ambulacral areas and poriferous zones; the plates of the tubercular columns are deep, there being only from six to seven plates in each column; the areolas are large and circular, especially above, but they incline towards an oval from below⁷; their margins are surrounded by a prominent scrobicular circle of fifteen or sixteen well-spaced-out granules (fig. 2), each of which is raised on an oval, shield-like base. In consequence of the size of the areolas in the upper part of the areas, the scrobicular circles of the two uppermost pairs closely approximate;

but from this point to the peristome there is a considerable inter-tubercular space, which is filled up with miliary granules of different sizes ; those nearest the areolas are raised on small basal elevations, which alternate with those of the scrobicular circle, and the rows internal to them diminish in size as they approach the median sutural line, where they become quite miliary : the mammillary bosses rise from a wide base (fig. 2 g); the three or four lower pairs have smooth summits, and the two or three upper pairs only are crenulated; the crenulations, however, are by no means either deeply sculptured, or very persistent in different specimens ; the tubercles are large, and are raised on a slightly contracted neck; the perforation in the hemispherical head has the form of an oblong slit, which passes through the head, and extends to the summit of the boss.

The mouth opening is large, and the peristome has a pentagonal form (fig. 2 b). In specimen b, it measures nine tenths of an inch in diameter, that of the equatorial diameter being two inches and two tenths ; the primary tubercles in the vicinity of the peristome are large and well developed, although smaller than those on the sides and upper surface of the test; the minute tubercles at the base of the ambulacral areas are only a little larger than the marginal granules of these areas.

The apical disc is absent in all the specimens I have examined. It was of considerable size; the diameter of the opening in specimen b being -j-^ths of an inch.

The spines are of three kinds, the primary, the secondary, and the tertiary. (PI. II, fig. 2 d, e,f.) The primary spines or radicles are very elegant bodies, and as they are often preserved in the Corallian stage, when the test to which they belonged is not discovered, a knowledge of them is of stratigraphical importance to the student of the Jurassic rocks. The concave articulating cavity has a deep pit in its centre (fig. 2 e) for the insertion of a ligament, and the rim of this acetabulum is surrounded with a circle of moniliform crenulations; the head is small, and is surrounded by a narrow ring, nearly smooth, and covered only with a microscopic milling of longitudinal lines; the ring is midway between the rim of the acetabulum and the point where the head articulates with the neck (fig. 2 e); the neck is short, and is covered with fine longitudinal lines ; it soon expands to form the body of the spine, the thickest part of which is just beyond the neck, from whence the stem gradually tapers to the apex, which is always more or less truncated (fig. 2 d); the stem is covered with small granulations, very uniform in size, and regularly disposed in longi­tudinal rows, forming from twenty to thirty lines of tubercles on the body of each spine, the number of the rows varying in different spines; the tubercles of the adjoining rows alternate, so as to produce a quincuncial arrangement; and the tubercles of each series are connected together by a calcareous filament which passes from one tubercle to another; the tubercles are all inclined towards the apex of the spine, and many of them terminate in short, prickly processes, which have their points directed forwards; the surface of the spine between the rows of granules is covered with numerous longitudinal lines: at the summit of the spines the granules coalesce, forming so many plates, which expand, and produce a radiated or star-like disc at the truncated extremity thereof. Some of the spines attain the length of two inches and three quarters. The secondary and tertiary spines are short and spatulate (fig. 2), and their surface is covered with fine longitudinal lines.

Affinities and differences.—In the form and structure of the test in general, Cidaris florigemma resembles Cidaris Blumenbachii, marginata^ coronata, and monilifera, but it is distinguished from all these forms by its greater height, and a consequent increase in the number of plates in the tubercular columns $ Cidaris marginata, coronata, and monilifera having five plates in each column, whilst Cidaris florigemma has from six to seven. In the plates on the upper part of the test of these species, the miliary zone is much wider, and the circles of areolar granules are likewise separated by many rows of miliary granules^, which are altogether wanting in Cidaris florigemma. The ambulacral areas in Cidaris marginata^ coronata, and monilifera have four distinct rows of small, nearly equal-sized granules, whilst in Cidaris florigemma the two marginal rows alone are well developed throughout.

Cidaris florigemma is distinguished from Cidaris Fowleri by the narrowness of its ambulacral areas, and by the size and prominence of the marginal granules; the

poriferous zones are likewise very much narrower, and the pores are smaller and set closer together; the inter-ambulacral areas are wider, whilst the miliary zone is narrower, the scrobicular circles are likewise much more prominent, and have larger granules, raised on distinct eminences; the smooth summits of the mammillary bosses of the lower tubercles, and the faint crenulations on those of the upper ones, form a striking contrast to the broad, deeply crenulated summits of the mammillary bosses in Cidaris Fowleri.

The same group of characters which serve to distinguish Cidaris florigemma from Cidaris Fowleri form the diagnosis between it and Cidaris Orbignyana.

Cidaris florigemma resembles Cidaris Smithii, Wright, with which it is occasionally associated in the same rock in Wiltshire and Yorkshire, in the general form and height of the test, but it is distinguished from this much rarer species by having fewer tubercles in the inter-ambulacral areas, and much more prominent scrobicular circles around them; Cidaris Smithii having ten primary tubercles in each column, and the granules of the scrobicular circles not being much larger than those filling the miliary zone; the ambulacral areas are likewise narrower, and the poriferous avenues are narrower and deeper; the spines, likewise, are longer, narrower, and differently sculptured.

     The primary spines of Cidaris florigemma most nearly resemble those of Cidaris coronafa, but their length, and the regularity of their rows of granules, serve to distinguish them from those of that species. The only other species of Cidaris with which it is necessary to compare them, is that of Cidaris Smithii, which sometimes occurs with Cidaris florigemma in the same rock in England. Although the tests of these two species resemble each other when of the same size, still the spines show that they belong to two distinct groups of urchins, the stems of Cidaris florigemma being thick and massive, whilst those of Cidaris Smithii are long and slender, tapering very gradually from neck to point; the surface is covered with elevated longitudinal ridges, covered with sharp, forward-directed prickles ; these spines are sometimes nearly twice the length of those of Cidaris florigemma. (PI. V, fig. 5.) The test of Cidaris Bhmenbachii has the areolas deeply excavated; the bosses not very prominent, the summits all sharply crenulated, and the tubercles small; the granules forming the scrobicular circle are not larger than those of the small granulation filling the miliary zone. These characters are so completely diagnostic, that it is impos­sible to mistake the true German form for Cidaris florigemma, when the two urchins are placed side by side for comparison. If to these characters of the test, however, are added those obtained from the spines, we leam how entirely distinct Cidaris Blumenbachii is from Cidaris florigemma.

     Judging from the spines figured by Goldfuss, Agassiz, Roemer, and Cotteau, this species must have had a wide European area of distribution, as its test or spines have been collected in the Coral Rag of different parts of Germany, Switzerland, and France.

     History.—The history of this species has been given with so much detail in th^ introductory remarks, that it is unnecessary to reproduce the facts under this section.

NDLR : original footnotes :

^* Plott's  "Natural History of Oxfordshire," p. 125

^** "Synopsis des Echinides Fossiles,^" p. 5.