250 Mr. r. M'Coy on some new Palceozoic Echinodermata. 



verse suture between the first and second series of supra-basal 

 plates nearly medial; base flattened; surface minutely gra- 

 nulated. Length 3 lines, width 3 lines. 

 If we suppose the lower third abruptly cut off a P. ellipticus, 

 we should have a good idea of this little species, which agreeing 

 with the above in most characters is distinguished by its small 

 size, more tapering ambulacra, greater proportional width and 

 wide base. 



Rare in the carboniferous limestone of Derbyshire. 

 [Col. University of Cambridge.) 



Codaster (M'Coy), u. g. 

 Etym. KOiScov, tintinnahulum, and aarrjp, stella. 

 Gen. Char. Cup conical, with the upper part broad, flat, trun- 

 cate ; pelvis deep, conical, of three pieces, one tetragonal and 

 two pentagonal, each having its inner apex 

 notched to form part of the round columnar 

 canal ; on the upper edges of these rest five 

 large equal first supra-basal plates which reach 

 to the truncated summit, to which from their 

 mesial gibbosity they give a pentagonal out- 

 line ; in the centre of this superior disc the p]a(. terminal disc 

 mouth seems situated, and from it five promi- of Codaster. 

 nent, minutely porous pseudambulacra diverge, 

 one to each angle, each being placed on a thick tapering ridge 

 divided by a mesial sulcus ; from the re-entering angles of those 

 ridges four other thick, rapidly tapering ridges proceed, one 

 to the middle of each of four of the straight sides, each ridge 

 at its thick, oral end shows an obscure impression, probably 

 of the ovarian pores ; the fifth space is without a ridge, being 

 occupied by a large, ovate or lozenge-shaped (? anal) opening ; 

 the depressed, triangular intervening spaces are marked with 

 coarse, rough parallel strise nearly coinciding in direction with 

 the pseudambulacral ridges, and converging to the second set 

 of ridges ; the impressed lines between these strise seem punc- 

 tured, the fifth (? posterior) space is without sulcation. 



These strange and beautiful forms, the 'bell-stars,' as they 

 may be called, are obviously allied to Pentremites (taking P. Der- 

 biensis, florealis, ohlongus, ellipticus, and such like as the types of 

 the genus), from which they differ in having the small basal 

 plates enormously developed into a conical pelvis, and having the 

 pseudambulacra entirely confined to the capital plates (which here 



found by MM. Roemer and Yondell (Bulletin de la Soc. Geol. de France 

 for 17th April 1848) to be really the alimentary canals of a double row of 

 little jointed tentacles resembling I imagine those of Pseudocrinites. 



