from the Island of Malta. 79 



the " faluns bleus de Narrosse," and adds that it is found like- 

 wise at Paris, Montpellier ?, Bordeaux, and the Vicentin : Des- 

 rnoulins adds St.Paul-trois-Ch&teaux (Drome) as another locality. 



Genus CONOCLYPUS (Agassiz, 1839). 



Test thick, hemispherical or oval, and always much elevated ; 

 ambulacral areas above long, wide, converging at the summit, a 

 little contracted below ; mouth median, symmetrical, pentagonal, 

 and surrounded by five large lobes ; base flat, basal portion of 

 the ambulacra with poriferous zones around the mouth-opening ; 

 anus inframarginal, sometimes transversely oblong. The spe- 

 cies are all fossil, and belong mostly to the tertiary rocks : one 

 is found in the Maestricht chalk. This genus is nearly allied to 

 Echinolampas. The character upon which M. Agassiz relied as 

 diagnostic between Conoclypus and that genus, the direction of 

 the anus, which is stated* to be elongated in the antero-posterior 

 diameter in Conoclypus, and in the transverse diameter in Echi- 

 nolampas, does not hold good in all the species. 



Conoclypus plagiosomus, Agassiz. 



SYN. Conocyplus playiosomus, Agassiz and Desor, Cat. rais., Ann. 

 Sc. Nat. 3rd series, torn. vii. p. 168. 



Test thick, large, highly convex ; border acute ; outline round, 

 inclining to oblong, being slightly compressed on the sides ; 

 ambulacral areas narrow, even with the interambulacra ; pori- 

 ferous zones very narrow ; the inner and outer pores nearly 

 equal in size, and extending through three-fourths of the 

 areas; base concave; mouth nearly central, with large oral 

 lobes ; anus large, transversely oblong and inframarginal. 



Dimensions. Antero-posterior diameter 6 inches, transverse 

 diameter 5j% inches, height 3 inches. 



Description. This noble Urchin has been mistaken for C. 

 conoideus, Lamk., as in form, size, and some of its general cha- 

 racters it resembles that type species ; but the eye of the prac- 

 tised zoophytologist detects, in the structure and narrowness of 

 the poriferous zones, an organic character sufficient to enable 

 him to separate it from that species. The general outline of the 

 base is round, inclining to oval from the gentle compression of 

 the sides thereof; the dorsal surface is much elevated and highly 

 convex, and the vertex is situated in front of the centre of the 

 dome ; the ambulacral areas are nearly one-fourth the width of 

 the iuterambulacral areas at the border, and are level with them ; 

 they are nearly of a uniform width throughout, becoming lan- 



* Ann. Sc. Nat. torn. vii. p. 1' 



