498 MOLLUSCA 



PHILINE Ascanias. Shell with a rudimentary spire, white, translu- 

 cent, oval; animals slug-like; radula with no central teeth; foot about 

 two-thirds the length of the body and obliquely truncated : 20 species. 



P. quadrata (Wood). Shell 5 mm. long, 3.5 mm. wide, with 2 to 3 

 whorls, squarely globose: New England north of Cape Cod, in rather 

 deep water; Europe. 



P. lima (Brown). Shell with 3 to 4 whorls, elongate, broadest ante- 

 riorly, 3.5 mm. long, 2 mm. wide, reddish in color: New England north 

 of Cape Cod; Europe. 



FAMILY 6. LIMACINIDAE. (PTEROPODA THECOSOMATA.) 



Shell and mantle present ; shell snail-like, minute, with a left-handed 

 spiral and an operculum ; ctenidium and eyes absent ; 1 pair of tentacles ; 

 mantle cavity, with anus and other openings on right side; 2 large fins 

 present, these being the epipodia, which have extended around the dorsal 

 side of the head : 2 genera and about 19 species, which are pelagic, prin- 

 cipally in the northern seas. 



Fig. 759 Fig. 760 Fig. 761 



Fig. 759 Limacina arctica (Leunis). Fig. 760 Cavolinia trispinosa (Dall). 1, gill, 

 Fig. 761 iCreseis conica (Dall). 



LIMACINA Cuvier. Shell transparent, with a low spiral and a wide 

 umbilicus: several species in the Arctic and Antarctic seas, which form 

 an important food of whales. 



L. arctica (Fabricius) (Fig. 759). Whorls of shell 6; spire low; 

 umbilicus wide ; width 4 mm. : Arctic seas, south to New Jersey. 



FAMILY 7. CAVOLINIIDAE. (PTEROPODA THECOSOMATA.) 



Shell and mantle present; shell not spiral, but symmetrical, straight 

 or curved, without operculum; ctenidium and eyes absent; 1 pair of ten- 

 tacles ; mantle cavity ventral ; 2 large fins present as in previous family : 

 about 50 species, all of which are pelagic. 



1. CAVOLINIA Abildgaard (Hyalea Lamarck). Shell globular, with 

 3 long sharp spines posteriorly; aperture contracted with a slit on each 

 side, through which long appendages of the mantle pass : 10 species. 



C. trispinosa (Lesueur) (Fig. 760). Length 10 mm.; median spine 

 as long as the body; lateral spines only a third as long: Atlantic coast. 



