GASTROPODA 505 



1. Alderia Allman. Body elongate, without tentacles; head with 

 lobes at the side; anus dorsal, posterior: 4 species. 



A. harvardiensis (Agassiz) (Fig. 768). Body square and broad in 

 front, tapering behind; cerata short, aiTanged in 6 or 7 clusters on each 

 side with 2 in each cluster; color brownish-yellow; length 12 mm.; 

 width 4 mm.: in shallow pools, north of Cape Cod; often common. 



2. Tergipes Cuvier. Foot rudimentary; cerata in a single row 

 on each side; tentacles cylindrical: several species. 



T. despectus Johnston. Four club-shaped cerata on each side; 

 dorsal tentacles long, oral tentacles short: Long Island Sound north- 

 wards; often abundant on hydroids in shallow water. 



Family 2. ELYSIIDAE. 

 Body without cerata, but ciliated, and with 2 lateral ridges, con- 

 taining hepatic cseca; radula with a single series of strong teeth; eyes 

 on the sides of the head; anus median or latero-dorsal : 15 species. 



Fig. 768 Fig. 769 Fig. 770 



Fig. 768 — Alderia harvardiensis (Gould). Fig. 769 — Elysia chlorotica (Gould). 

 Fig. 770 — Elysia catula (Gould). 



1. Elysia Risso. Body elliptical, depressed; wing-like ridges wide; 

 2 rather short, thick tentacles: 7 species. 



E. chlorotica (Agassiz) (Fig. 769). Body slender, bright green in 

 color, dotted with white and red spots, 40 mm. long, 8 mm. wide; ridges 

 broad, folding over the back, overlapping when the animal crawls, and 

 expanded, leaf-like, when it swims: New Jersey to Boston, in shallow 

 and brackish water; often abundant. 



E. catula (Ag.) (Fig. 770). Bocly elongate, brownish-green in 

 color, with a few whitish spots, 6 mm. long and 2 mm. wide ; ridges when 

 folded do not overlap: New Jersey to Boston; common among eel 

 grass and shallow water. 



Family 3. LIMAPONTIIDAE. 



Body minute without lateral expansions or cerata; sides of head 

 with ridges; anus median and posterior: 6 species. 



LiMAPONTiA Johnston. Eyes on the lateral cephalic crests: several 

 species. 



