304 Royal Society : — 



links, that it is difficult to tell where the one begins and the other 

 ends. It is possible that they ought to be regarded as varieties, and 

 lumped together under Lamarck's name, E. acutus. 



6. E. microstoma, n. sp. 



Although I have great hesitation at present in proposing an addi- 

 tion to the genus Echinus, I feel compelled in the meantime to 

 separate this very distinct form with a thin depressed test, a remark- 

 ably large periproct, and a small peristome with the edge markedly 

 curved inwards and a uniform vivid red colour. E. microstoma is 

 very abundant from 150 to 400 fathoms off the west coasts of Scot- 

 land and Ireland. 



Sphcerechinus, Desor. 

 1. S. esculentus, L., sp. 



A marked variety, with a tall narrow test and white spines, in deep 

 water. 



Toccopneustes, Agassiz. 



1. T. dr'6bachiensis,W\!i\\er. 



Of this species it seems to me that T. pictus, Norman, and T.pal- 

 lidus, G. O. Sars, can only be regarded as varieties. It is generally 

 distributed at depths beyond 100 fathoms. 



2. T. brevispinosus, Risso, sp. 

 Shallow water on the coast of Spain. 



Psammechinus, Agassiz. 



1. P. miliaris, Lam., sp. 



2. P. microtuberculatus, Ag. 



Cassidulid^. 

 Neolmapas, A. iVgassiz. 

 This genus, with a nearly central pentagonal mouth and a tolerably 

 distinct floscelle, with the anal opening at the bottom of a deep pos- 

 terior groove excavated in a kind of projecting rostellum, with narrow 

 ambulacral arese and a small compact group of apical plates, must 

 be referred to the Cassidulidse ; but it differs from all known genera 

 of the family, living or extinct, in having no trace of a petaloid 

 arrangement of the ambulacra, which are reduced on the apical sur- 

 face of the test to a single pore penetrating each ambulacral plate, 

 and thus forming a double row of alternating simple pores for each 

 ambulacral area. 



1. N. rostellatus, A. Ag. 



I believe I am correct in referring to this species a single specimen 

 dredged at the mouth of the English Channel. It is upwards of an 

 inch in length, and therefore nearly double the size of the examples 

 procured by Count Pourtales in depths of from 100 to 150 fathoms in 

 the Strait of Florida. 



ClYPEASTRIDjE. 



Echinocyamus, Van Phelsum. 

 1. E. angulatus, Leske. 

 Generally distributed, but not found living beyond 150 fathoms. 



