^^4< Dr. T. Wright on Fossil Echinoderms 



the following characters : — S. eurynotus is broader and more 

 depressed before, and is not proportionally so high behind as 

 S. canaliferus ; the antero-lateral ambulacra are more divergent, 

 and the postero-lateral pair are proportionally longer in S. eury- 

 notus than in S. canaliferus. The single ambulacrum is about 

 the same depth as the pairs, and has the pores in a single file in 

 S. eurynotus, whereas in S. canaliferus this area is much deeper, 

 and the pores are not in single file, but are crowded together, so 

 that they form three rows in a part of the zone ; the tubercles 

 of the base are much larger in the living than in the fossil 

 species. S. eurynotus is distinguished from S. Parkinsoni by 

 its /-shaped ambulacra being less divergent, and the position of 

 the apical disc, which is much nearer the posterior border in S. 

 eurynotus ; the anterior ambulacrum is likewise much wider and 

 deeper in that Urchin than in S. Parhinsoni : the great develop- 

 ment of the single interambulacrum, and breadth of the pos- 

 terior border in ^. Desori sufficiently mark that species as 

 widely distinct from S, eurynotus. 



Locality and position. — Collected in bed No. 4, the calcareous 

 sandstone at Malta ; we have it also from Santa Manza, Corsica, 

 sent us by M. Michelin ; it has likewise been found in the Ter. 

 moyen de Perpignan, Cagliari. 



Schizaster Desori, Wright, n. sp. PI. VI. fig. 3 a-c. 



Test cordate, broad and much depressed before, narrow and 

 much elevated behind ; ambulacral areas long, straight, and 

 very divergent ; peripetal fasciole forms an acute angle on the 

 anterior interambulacra ; apical disc situated at the posterior 

 third of the dorsum ; angle of the antero-lateral ambulacra 

 44° ; angle of the postero-lateral pair 60° ; posterior border 

 truncated obliquely downwards and inwards ; sternal portion 

 of the interambulacrum tumid and prominent at the base, 

 amounting almost to a deformity. 



Dimensions. — Antero-posterior diameter 2 j% inches, transverse 

 diameter 2^-q inches, height at the deepest part ly^^j inch. 



Descinption. — This remarkable Urchin wants the symmetrical 

 proportions of the other Schizasters met with in the same rocks ; 

 it is rounded and broad before, and tapers into a narrow wedge- 

 shape process behind ; the dorsal surface inclines forwards at an 

 angle of 17°; the ambulacral areas are long. The single anterior 

 area compared with S. eurynotus is narrow, and of a uniform 

 width ; it is ly^^ inch in length from the apical disc to the 

 fasciole ; there are twenty-four pairs of pores in the avenues, 

 the external being much larger than the internal row, although 

 this is properly speaking a generic character. The antero-lateral 



