502 MOLLUSCA 



pinnate gills, surrounded by 8 to 12 long projections; all tentacles and 

 projections tipped with yellow: New England north of Cape Cod, often 

 common under stones. 



FAMILY 2. DOBIDIDAE. 



Mantle large, covering the head and without marginal appendages; 

 integument generally very spiculose; rhinophores laminate and retrac- 

 tile; anterior tentacles small; gills usually retractile: 9 genera. 



Key to the genera of Dorididae here described : 



G! Gills retractile ' 1. DORIS 



a. Gills not retractile. 



&! Gills pinnate and simple 2. ONCHIDORIS 



& a Gills bipinnate 3. ACANTHODORIS 



1. DORIS L. Body depressed, often with dorsal tubercles; gills 

 branched or feathered, united at the base, and retractile; mouth with 2 

 oral lobes: 150 species; cosmopolitan. 



D. repanda Alder and Hancock. Body broad, light- 

 colored, covered with minute white tubercles; mantle ex- 

 panded beyond the foot ; gills form a star of about 10 pin- 

 nate plumes ; length 15 mm. ; width 12 mm. : New England 

 north of Cape Cod, under stones at low-water line ; Europe. 



D. bifida Verrill (Fig. 765). Body broad and oval, 

 purplish-brown in color, speckled with white, 25 mm. long, 

 12 mm. wide ; back very convex, with papillae ; gills with 7 

 Doris Wflda bipinnate plumes : New England from Long Island Sound 

 to Eastport, under stones at low-water mark. 



2. ONCHIDORIS Blainville. Body depressed; head with a veil in 

 place of oral tentacles; gills pinnate, set in a circle and non-retractile: 

 23 species. 



0. bilamellata (L.). Body elliptical, brownish or pink in color, 

 covered with short, unequal papillae; gills 20 to 25 in number, slender 

 and arranged in an oval; length 25 mm.; width 12 mm.: Atlantic coast, 

 north of Cape Cod; often common; Europe. 



0. pallida (Agassiz). Body elongate, cream-colored, covered with 

 large mushroom-like tubercles; gills form a star of 7 or 8 broad plumes, 

 which are retractile; 12 mm. long, 6 mm. wide: Cape Cod northwards, 

 from low-water mark to 30 fathoms; Europe. 



3. ACANTHODORIS Gray. Body convex, covered with soft papillae; 

 oral lobes united to form a veil; gills united at the base and non- 

 retractile: 4 species. 



A. stellata Verrill. Body broad, narrower behind, covered with 

 small pointed papillae; gills composed of 7 bipinnate plumes; color 



