BEITISH FOSSILS. 



Monis 3 Catalogue it is erroneously stated to belong to the " Upper" 

 Chalk, and in Desor's Synopsis to the " Gres vert sup/' 



Explanation of the Plate. 

 Fig. 1. Side view, natural size. 

 Fig. 2. Upper view, or dorsal surface. 



Fig. 3. One of the interambulacral plates, and part of an ambulacrum, from the circum- 

 ference. 



Fig. 4. Apical disk, magnified. 

 Fig. 5, 6. Miliary spines, magnified. 



Note on some oilier Species of Cidaris found m British Stimta. 

 In Professor Morris's Catalogue three other species of Cidaris are enumerated, and 

 referred to the unpublished MSS. of Professor Forbes. 



Cidaris confluens Inf. O., Cheltenham. 

 C. dissimilis, L. Ch., Kent, Sussex. 

 C. Gaultina, Git., Folkstone. 

 The characters may be given as follows : — 



1. Cidaris dissimilis, Forbes, MS. Morris's Cat., 2nd. edit. p. 74. C. sceptrifera, 

 Forbes in Dixon, pi. 25. f. 3. 



Body small, 1 1 lines in diameter, 6^ lines high, resembling C. sceptrifera in general 

 character ; ambulacra narrow, flexuous, with six ranges of small granules ; inter- 

 ambulacral plates 4-5 ; areolae circular, wide apart, surrounded by distinct secondary 

 tubercles; principal tubercles prominent, slightly crenulated, — the lowest minute, the 

 uppermost rudimentary and without areolee ; miliary granules large and prominent. 

 Spines of two sorts; the largest above, 24 lines in length, slightly swelling above the 

 collar (2^ lines diameter), and then tapering to a fine point ; collar short, striated 

 finely; shaft granulated in lines; spines of lower surface very slender, 3-6 sided, 

 serrated at the angles ; spines of areolar circles 2 lines in length, compressed and 

 striated. 



Locality. — Grey Chalk, Dover. Collected by Messrs. Clarke, Dixon, and Taylor, 

 (now in Brit. Mus. and Mus. Pract. Geology). 



2. Cidaris conjluens, Forbes, MS. Morris's Cat., 2nd edit. p. 74. 



The specimen consists of four consecutive plates of nearly equal size, from one of the 

 interambulacral rows. The set measures 1 inch in length and ^ inch wide. The 

 areolse are 4 lines wide, and broadly confluent one with another ; the bosses promi- 

 nent and crenulated ; the lateral borders of the plates are narrow and uniformly 

 granulated. There are numerous fragments of spines in the same piece of rock ; 

 they appear to have been very long, slender, cylindrical, striated lengthwise, and 

 armed with a few large scattered prickles. 



Locality. — Inferior Oolite. Frome (not Cheltenham). 



3. Cidaris Gaultina, Forbes, MS. Morris's Cat., 2nd edit. p. 74. 



Detached plates of this species resemble those of C. vesiculosa (suhvesiculosa, D'Orb.) 

 from the Chalk. A plate from the upper part of the test has the areola surrounded 

 by a circle of secondary tubercles, but not depressed. The spines are like those of 

 C. vesiculosa, slender, elongated, and fluted, the ridges being more finely serrated ; 

 the collar of the spine is shorter than in C. vesiculosa. A broken spine 

 accompanying the plates has the end expanded and cup-like ; but in two other 

 perfect examples the extremities are simply contracted and truncated. 



Lc'Cality. — Gault, Folkstone. (Mus. Practical Geology. Presented by Edward 

 Clark, Esq.) 



