92 DR. GWYN JEFFREYS ON THE MOLLUSCA OF THE [Mar. 6, 



faint tinge of green : spire considerably raised : whorls 4, rounded 

 and convex ; the last occupies two thirds of the spire ; the first is very 

 small and abruptly twisted : suture very deep : mouth circular, with a 

 thin and slio;htly expanded lip : umbilicus rather narrow but deep : 

 operculum thin, having 6 or 7 whorls, the two outermost being pro- 

 portionally much larger than the inner whorls and divided by raised 

 ledges. L. 007.5, B. 0-1. 



'Porcupine' Exp. 1869: St. 16, A single but living specimen. 



The shell is more conical and thinner than C. trocho'ides ; the 

 spire is more raised, and the sculpture very different. 



1/ 9. Cyclostrema VALVATOiDEs\ Jeffreys. (Plate XIX. fig. 3.) 



Shell obliquely helical, rather solid, opaque and glossy : sculp- 

 ture none exce])t slight and irregular lines of growth : colour 

 whitish, with a faint tinge of yellow : spire depressed : whorls 4, 

 rounded and swollen ; the last expands outwards, and occupies about 

 three fourths of the spire ; the top whorls are flattened : suture 

 deep : mouth very large and circular, with a short and obtuse angle 

 at the upper corner ; the lip is considerably reflected or folded 

 back: umbilicus small and shallow. L. 0'075, B. 0'125. 



'Porcupine' Exp. 1870: Atl. St. \7a. A single but perfect 

 specimen. 



The description shows that this is a very distinct and peculiar 

 species. It certainly belongs to the present genus, although having 

 the aspect of a Valvata. 



v" 10. Cyclostrema SIMILE ^ Jeffreys. (Plate XIX. fig. 4.) 



Shell orbicular, compressed above and below, rather thin, 

 opaque, but glossy ; sculpture none : colour whitish : spire much 

 depressed : whorls 4k, rounded and convex ; the last occupies about 

 one half of the shell ; first whorl spiral : suture wide and deep : 

 mouth nearly circular, but slightly truncate on the inner side ; edges 

 thin : umbilicus open and deep, exposing part of the penultimate 

 whorl. L. 0-025, B. 0-0.5, 



'Porcupine' Exp. 1870: Atl. St. 16, 17a. Three specimens. 



Smaller than C. valvato'ides, but apparently full-grown ; the spire 

 is more depressed, the suture deeper, the last whorl not so dis- 

 proportionately large, the mouth smaller with simple and not re- 

 flected edges, and the umbilicus is much more open. 



i/ 11. Cyclostrema affine^ Jeffreys. (Plate XIX. fig 5.) 



Shell resembling a species of the Margarita section of Trochus, 

 turreted, rather thin, semitransparent and glossy : sculpture none : 

 colour clear white : spire raised : lohorls 4, swollen ; the last occupies 

 about two thirds of the shell ; first whorl bulbous : suture narrow 

 but deep : mouth slightly angulated on the upper side, where it 



' Shaped like a Valvata. 



- Similar, i. c. to C. valvato'ides. 



' Allied, i. c. to species of TS-ochv.s. 



