ACERA. 431 



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

 curved at the further extremity: imier 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. 7iana. Undistinguishable except by its dwarf size. 



Habitat : Oozy ground and mud-flats (often among 

 Zostera) in tlie 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*^ 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 ^gean ; 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 w^eather, 

 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 Acer a having eyes was, I believe, 

 first noticed by me in the '^Annals and Magazine of 

 Natural History ' for September 1859. The head bears 

 a fanciful resemblance to the snout of a restored Dino- 



