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, nu. 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 tuberculigerous 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 1,8, inch, height 1 inch ? 
Description— This Urchin is so much crushed that it is im- 
possible to describe its outlme. 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 ;8,ths of an inch in length : 
the postero-laterals form an angle of 55°; they are ;°,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. latus, 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 the 
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 
