GASTROPODA 499 



2. Creseis Rang. Shell conical, slender, pointed, straight or 

 slightly curved : 6 species. 



C. conica Eschscholtz (Fig. 761). Length 12 mm.; diameter 2 mm.: 

 Atlantic coast. 



Division 2. APLYSIOIDEA. 



Shell reduced or absent ; head without cephalic disc- and with 2 pairs 

 of tentacles; epipodia present, which arise from the sides of the body 

 and not the foot; osphradium present: 6 families, all but the Aplysiidae 

 being Pteropoda Gymnosomata, or shell-less pteropods. 



Key to the families of Aplysioidea here described : 



«! Shell present ; animals live on seaweed 1. Aplysiidae 



a. Shell absent ; animals pelagic (pteropods) 2. Clionidae 



Family 1. APLYSIIDAE. 



Sea hares. Body large; shell rudimentary and internal; animal 

 slug-like, with the anterior angles of the head extended into 2 large 

 tentacular folds, behind which are a pair of eyes and behind these the 

 rhinophores; epipodia, which are large lobes, turn up over the back: 

 7 genera and numerous species; cosmopolitan; mostly large, brightly 

 colored slugs, which secrete a reddish fluid from the mantle wrongly 

 supposed by many to be poisonous. 



Aplysia L. Animal swollen behind, with a long neck and head; 

 shell flexible; epipodia mobile and used for swimming: 50 species. 



A. protea Rang. Length 16 cm.; color variable, yellow or green, 

 with ring-shaped spots of black, red, and green: common in the West 

 Indies, also on the Florida coast. 



A. calif ornica Cooper. Length up to 37 cm.; color 

 gray or greenish, purple on the sides, covered with brown 

 lines and blotches; epipodia behind the middle: Monterey 

 to San Pedro. 



Family 2. CLIONIDAE. (Pteropoda Gymnosomata.) 



Shell and mantle absent; body fusiform; head dis- 

 tinct, with 2 pairs of tentacles, the hinder of which bears 

 ejes ; foot represented by a pair of fins which spring from 

 the base of the neck; between the base of the fins the 

 rudiment of the median portion of the foot; gill absent; 

 proboscis generally with suckers or with lateral lobes which bear suckers : 

 14 genera; pelagic. 



Clione Pallas. With the characters of the family: 10 species. 



C. limacina (Phipps) (Fig. 762). Body tapering to a point behind, 

 35 mm. long, pale blue in color and hyaline; fins triangular: Arctic 



