from the Island of Malta. 101 



that island, sent us by M. Michelin of Paris ; we consider the 

 peculiar arch-like arrangement of the peripetal fasciole, with the 

 marginal; as good generic characters whereby to form a distinct 

 genus. 



Pericosmus excentricus, Wright, n. sp. 



Test oblong, highly convex above, slightly so below; apical disc 

 very excentral, near the anterior border ; ambulacra in shallow 

 depressions ; single ambulacrum slightly grooves the anterior 

 border ; antero-laterals nearly transverse ; postero-laterals in- 

 cline at 55 ; peripetal fasciole narrow and undulating ; mar- 

 ginal fasciole narrow and low on the border ; tubercles on the 

 upper surface small, close-set, and nearly all of the same size ; 

 a few larger ones on the anterior interambulacra ; anus large 

 and situated high on the border; mouth-opening wide in the 

 anterior third, surrounded by five poriferous petaloid zones ; 

 sternal portion of the interambulacrum convex, with close-set 

 imbricated tuberculigcrous plates; basal portions of the inter- 

 ambulacral pairs with larger tubercles, wider apart, and more 

 irregular than those of the dorsum. 



Dimensions. Antero-posterior diameter 2 inches, transverse 

 diameter ly 8 ^ inch, height 1 inch ? 



Description. This Urchin is so much crushed that it is im- 

 possible to describe its outline. The ambulacral areas form 

 shallow depressions, and the single area slightly grooves the an- 

 terior border : the antero-laterals are nearly transverse, their in- 

 clination being forwards ; they are -j^ths of an inch in length : 

 the postero-laterals form an angle of 55; they are y^ths of an 

 inch long. The crushed state of the test makes it impossible to 

 count accurately the pores, or give the breadth of the areas ; the 

 apical disc, with four genital pores, is very small and remarkably 

 excentrical, being very near the anterior border ; the peripetal 

 fasciole is narrow, angular and undulating, and instead of sur- 

 rounding the anterior part of the antero-lateral ambulacra, as in 

 P. latuSy it descends from them and joins the marginal fasciole 

 below their base, so that the anterior sides of the antero-laterals, 

 and the single ambulacrum, want the peripetal fasciole. The 

 specimen before us is so much crushed, that we cannot trace the 

 band continuously all round the test, so as to describe its course 

 with accuracy ; it is possible that this species may form tin- 

 type of a distribution of the fascioles distinct from any that is yet 

 known. We have stated enough to show, that at least in this form 

 there is a considerable deviation from the normal arrangement. 

 The anus is large and oval, and near the dorsum; the mouth is wide 

 and bilabiate, and situated near the border; the sternal portion 

 of the interambulacrum is slightly convex, and thickly covered 



