GASTROPODA 503 



variable, often purplish; length 25 mm.; width 12 mm.: Long Island 

 Sound and northwards, under stones at low-water mark. 



DIVISION 3. ^GOLIDIOIDEA. 



Simple unbranched cerata on each side, into which liver projections 

 extend and which often contain nematocysts; anus usually on right 

 side: 9 families. 



Key to the families of ^Eolidioidea here described : 



fli Numerous cerata, in transverse rows 1. JEoLiDiDAE 



a 2 One longitudinal row of cerata on a side 2. DOTONIDAE 



FAMILY 1. ^OLIDIDAE. 



Cerata arranged in transverse rows along the body, which contain 

 nematocysts, which, however, have been introduced with the hydroids 

 on which the animals feed; no spicules in integument and no mantle; 

 tentacles non-retractile; anus on the right side: 100 species, the animals 

 feeding largely on hydroids and bryozoans. 



Key to the genera of JEolididae here described: 



Oj Body broad, being at least a third as broad as long 1. 



fl-a Body usually less than a quarter as broad as long. 

 &! The 2 pairs of tentacles unequal in length. 



G! Front angles of foot not prolonged 2. 



c 3 Front angles of foot prolonged 4. COBYPHELLA 



6 2 The 2 pairs of tentacles of equal length 3. FLABELLINA 



1. JEoLis Cuvier. Body ovate; cerata cylindrical and numerous, 

 extending along the entire back; 2 pairs of cylindrical tentacles: 

 numerous species. 



A. papillosa (L.) (Fig. 766). Body broad, depressed, 

 tapering behind, gray or orange-colored, spotted with 

 brown or white; cerata crowded, arranged in 12 to 20 

 imbricated oblique rows on each side and 10 or 12 in 

 a row; length 7 cm.; width one-third the length: Rhode 

 Island to Arctic Ocean, among hydroids and under stones 

 between tide lines ; Europe. 



2. ^OLIDIA Cuvier. Tentacles of unequal length; 



Fig. Too 



cerata compressed, in transverse, rather distant rows: 4 JKolis papillosa 



(Gould), 

 species. 



A. pilata (Gould). Body elongate, 38 mm. long, 6 mm. wide, pale 

 drab in color with a mid-dorsal, interrupted carmine stripe margined 

 with silvery dots; cerata fusiform, in 5 groups: Long Island Sound to 

 Massachusetts Bay. 



A. diversa (Couthouy). Body elongate, tapering to a point, pale 

 yellow in color; oral tentacles long and slender; dorsal tentacles shorter; 



