GASTROPODA 501 



DENDRONOTUS Alder and Hancock. With the characters of the family. 



D. arborescens (0. F. Miiller) (Fig. 763). Color pale or red with 

 brownish or whitish 

 spots; cerata trans- 

 parent, 5 to 7 on a 

 side ; length 8 cm. : on 

 rocks and seaweed ; 

 circumpolar, south to 

 Rhode Island ; com- 

 mon in Casco Bay; Fig. 763 Dendronotus arborescens (Gould). 

 Europe. 



DIVISION 2. DOEIDIOIDEA. 



Anus median and posterior and surrounded by a circle of adaptive 

 gills into which the liver does not extend: 5 families. 

 Key to the families of Doridioidea here described : 



a t Mantle with lateral tubercles or appendages 1. POLYCERIDAE 



a a No lateral tubercles or appendages 2. DORIDIDAE 



FAMILY 1. POLYCEEIDAE. 



Body elongate, with a marginal ridge on each side bearing tubercles 

 or appendages; integument with spicules; rhinophores not retractile and 

 usually lamellate ; gills non-retractile and with lateral projections : about 

 8 genera. 



Key to the genera of Polyceridae here described: 



a^ Marginal ridge with short tubercles of nearly equal length 1. POLYCERA 



c a Marginal ridge with long appendages, some at base of rhinophores. 



2. ANCULA 



1. POLYCERA Cuvier. Body limaciform; mantle indistinct, forming 

 a projecting frontal velum and a tuberculated ridge along each side: 

 11 species. 



P. lessoni D'Orbigny. Length 30 mm.; color greenish; about 6 



long, finger-like tubercles on a side, tipped with yellow; a median row 



of tubercles also present; head with 6 projecting points on each side: 



Long Island Sound and northwards; Europe; common in Casco Bay 



from low water to 20 fathoms. 



2. ANCULA Loven. Body limaciform and 

 smooth ; head bearing tentacular projections at the 

 base of the rhinophores as well as one at side in 

 front, and also several surrounding the gills: 3 

 species. 



A. sulphurea Stimpson (Fig. 764). Body slender, 30 mm. long, 

 light brownish and transparent; rhinophores club-shaped; 3 branched, 



