GASTROPODA 503 



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

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



Division 3. -SIOLIDIOIDEA. 



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 JEolidioidea here described : 



fl^ Numerous cerata, in transverse rows 1. iEoLiDiDAE 



Ca 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 ^olididae here described: 



Oi Body broad, being at least a third as broad as long 1. ^^olis 



«2 Body usually less than a quarter as broad as long. 

 &i The 2 pairs of tentacles unequal in length. 



Ci Front angles of foot not prolonged 2. ^Ii^olidia 



Ca Front angles of foot prolonged 4. Coryphella 



&2 The 2 pairs of tentacles of equal length 3. Flabellina 



1. .^OLIS Cuvier. Body ovate; cerata cylindrical and numerous, 

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

 numerous species. 



A. papulosa (L.) (Fig. 766). Body broad, depressed, '''==^^^^^ 



tapering behind, gTay or orange-colored, spotted with j^j^ 



7,Tj 



brown or white; cerata crowded, arranged in 12 to 20 v^v,.^ »-* . 



imbricated oblique rows on each side and 10 or 12 in l>i'J^h'i;y 



a row; length 7 cm.; Avidth one-third the length: Rhode Shl®'^^) 

 Island to Arctic Ocean, among hydroids and under stones '\..\-^-^jrL 



between tide lines ; Europe. 



2. iEoLiDiA Cuvier. Tentacles of unequal length; 



Fig. (66 



cerata compressed, in transverse, rather distant rows: 4 JEoUs papulosa 



'- ' (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 

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



