FROM THE COK\L RAG. 817 



intimately soldered to the surrounding structures that I have as yet failed to detect them 

 with my compound microscope, provided with an inch object-glass ; but the elements 

 of the disc are, in general, united so entirely to the adjoining plates of the test in the 

 CoLLYRiTiD.E, that it is only in weathered specimens, or in those in which the shell has 

 passed into the condition of calcareous spar, that we can distinguish the separate pieces of 

 which it is composed. The tubercles on the sides and upper surface are small, and 

 arranged in tolerably regular lines on the plates. There are, in general, three rows 

 on each plate (fig. 1 e); those at the base are larger (fig. 1/), and more prominent ; they are 

 raised on prominent bosses, which are surrounded by areolas, and the intermediate spaces 

 are covered with close-set granules. 



Affinities and differences.' — The general outline of C. ovalis resembles C. ringens, but 

 is distinguished from it by the following characters. In C. ovalis., the highest point 

 of the back is near the anterior third, whilst in C. ringens, it is at the posterior third ; 

 in C. ovalis, the base is nearly uniformly convex, in C. ringens it is very much undulated ; 

 in C. ovalis, the apical disc is situated near the anterior third of the back, whilst in 

 C. ringens, it is nearly central. The single inter-ambulacrum, likewise, is not so 

 much developed ; the anal opening is larger, and higher up, and the anal valley is more 

 rudimentary in C. ovalis than in C. ringens. 



This species is distinguished from C. hicordatus, Leske, by the posterior ambulacra 

 always terminating in C. ovalis at or near the apex of the anal opening, whilst in 

 C. hicordatus, the apices of these areas terminate at a point about one third of the 

 distance between the vent and the disc. The same character, the proximity of the 

 apices of the posterior ambulacra to the anal opening, serves to distinguish C. ovalis 

 from C. elliptica. C. ovalis resembles C. analis, but in the former they are nearer the 

 vent than in the latter. It is highly probable, however, that this is a mere variety, and 

 not a specific difference. 



Locality and Stratigraphical position. — I have -collected this species in the marly vein 

 which traverses the upper ragstones of the Inferior Oolite, in the zone of Ammonites 

 ParJcinsoni, Sow., at Walditch Hill, near Bridport, where it was associated with Collyrites 

 ringens, and Holectypits hemisphcericus. It has been found by Mr. Walton in the same 

 zone at Charlcomb, near Bath, and by Dr. Bowerbank in the Cornbrash of Wilts, where 

 it is rare, as I only know of his solitary specimen from that formation. 



History. — First figured by Knorr, and afterwards figured and described by Leske as 

 Spatangites ovalis, in his edition of Klein's ' Echinodermata,' which figure was confused 

 with the Spatangites hicordatus of the same author. It was beautifully figured as 

 Disaster hicordatus by M. Desor, in his 'Monographic des Dysaster;' afterwards by 

 M. Cotteau under the name Disaster Rohinaldinus, in his ' Etudes des Echinides Fossiles,' 



