ACERA. 431 



on the upper part ; outer corner rounded ; inner corner in- 

 curved at the further extremity: inner lip consisting of a 

 rather thin glaze on the pillar and within the mouth : pillar 

 slightly folded, and projecting ; there is no umbilicus. L. 1-25. 

 B. 0-8. 



Var. nana. "[Indistinguishable except by its dwarf size. 



HABITAT : Oozy ground and mud-flats (often among 

 Zostera) in the laminarian zone, in many estuaries, and 

 along our southern, Irish, Scotch, and Zetlandic coasts ; 

 Walton-on-the-Naze (W. B. King) ; Orwell River 

 (Clarke); Scilly Isles (Lord Vernon); Guernsey (Han- 

 ley); Jersey (Dodd). It is gregarious. The variety 

 occurs in Lough Larne and Balta Sound at low-water 

 mark and in 3-5 f. (J. G. J. and M f Andrew); Norway 

 (Loven). Mr. Grainger found the typical form in the 

 Belfast deposit. The foreign distribution of this species 

 extends from Oxfjord in Finmark (Sars) to Vigo Bay 

 (M'Andrew), the French and Italian coasts of the Me- 

 diterranean, the Adriatic, and ^Egean ; depths recorded 

 2-20 f. 



A. bullata flits about, like a Pteropod, by means of 

 its ample and flexible foot-lobes. The account given by 

 Olivi of its swimming and migratory habits is very in- 

 teresting, and helps to explain the sudden appearance 

 and disappearance of certain marine mollusca in parti- 

 cular localities. " The fishermen call them sea-snails, 

 and assured us they were very lively in warm weather, 

 and sometimes quitted their shells ; this circumstance, 

 however, is to be doubted" (Montagu). Mr. Hynd- 

 man says that when touched they give out a purple 

 liquid. The fact of Acera having eyes was, I believe, 

 first noticed by me in the f Annals and Magazine of 

 Natural History ' for September 1859. The head bears 

 a fanciful resemblance to the snout of a restored Dino- 



