12 ECHINODERMS OF THE CRAG. 



tinctly indicated ; the avenues are sub-parallel, slightly radiating. The anus is 

 exceedingly small in proportion to the size. It is placed at two thirds of the distance 

 from the mouth to the margin. The strengthening buttresses are well developed 

 internally. 



The very small anus, its position, and the very minute and comparatively scattered 

 tubercles, easily distinguish this from any of its congeners. 



There are some small ovate specimens which appear to belong to a variety of this 

 species. 



A large example measures five twelfths of an inch in length by very nearly the same 

 in breadth, and one eighth in height. 



It occurs in the Coralline Crag of Ramsholt. 



Mr. Morris in his ' Catalogue,' gives the Coralline Crag of Suffolk, as the formation in 

 which Echinocyamus Suffolciencis occurs : this species was probably intended. 



4. Echinocyamus oviformis. Plate I, figs. 17 and 18. 



The test is ovate, tumid for the genus, remarkably rounded at the sides, and depressed 

 above. Its surface is covered with rather coarse tubercles. The mouth is placed on a 

 plane, or slightly concave ventral surface ; it is very large. The vent, though small in 

 comparison, is large in proportion to the dimensions of the test, and is placed on the 

 inferior slope of the terminal tumid margin, a position which at once distinguishes the 

 species from all our other British Ec/unoci/ami. 



This small species, of which I have examined as many as twelve examples, in the 

 cabinet of Mr. Searles Wood, has an immature aspect. Its characters are, however, 

 lunnistakcably peculiar. It is from the Coralline Crag of Sutton. 



The largest specimen measures two tenths of an inch in length by two twelfths in 

 breadth and one tenth in height. 



Gentis — EcHiNARACHNiDS, Van Phelsum. 



Discoid, depressed urchins, with open and not converging dorsal ambulacra. Their 

 mouths are small and circular. The vent is small and marginal. They have four genital 

 pores. 



One species, if not two, inhabit the North Atlantic now. It is with much doubt that 

 I refer the following fossils to this genus. 



l.'EcHiNARACHNius? WooDii. Plate II, fig. 5 and (same species?) fig. 6. 



The fragment of a nuich depressed, slightly convex ovate urchin, concave underneath, 

 with a sub-central mouth. Represented in Plate II, fig. 8. 



