366 CANCEL! ARIADiE. 



occupies a quarter of the whole length, and is furnished 

 with a fourth almost plain belt, below which the surface is 

 more or less flattened and compressed, and at most marked 

 with one or two remote and not very prominent spiral 

 riblets. The mouth occupies a quarter of the entire length 

 of the shell, and when perfect (a state in which it is seldom 

 obtained) is slightly longer than broad, and has a rounded 

 rhombic contour, the pillar lip which is dark, broadly 

 reflected, and devoid of sculpture forming a more or less 

 marked obtuse angle with the base of the penult turn, 

 whilst the sharp-edged outer lip, which is disposed to 

 expand, and advances at the anterior extremity, is pecu- 

 liarly arcuated. The sinus at the base of the aperture is 

 rather long ; the canal itself is not particularly so, but is 

 very distinct. Our largest example measured a quarter of 

 an inch only in length, and scarcely a line in breadth. 



We had once (on the west coast of Ireland) an oppor- 

 tunity of taking this animal alive, and of making a slight 

 sketch under unfavourable circumstances. The notes of 

 Mr. Clark furnish much fuller information, and the ob- 

 servations and beautiful drawings of Mr. Alder. Through 

 the kindness of Mr. Clark we have had an opportunity of 

 re-examining the animal. The head is rather short, com- 

 pressed, vertically cloven in front, and furnished with a 

 retractile proboscis. It is flanked by two rather short, 

 inflated, subrotund tentacula, which are not very divergent 

 and are somewhat triangular at their bases. Their tips 

 are obtuse or very slightly clavate ; they are frosted and 

 hyaline, and as if edged with a line of intense white. 

 The eyes are placed rather close together, towards the 

 centre of the tentacle-base. The mantle is loose, plain at 

 the margin, and has a fold or rudimentary siphon never 

 extended beyond the shell. The foot is rather long, 



