MANUAL OF NATUKAL HISTORY." 141 



each cross series, inner lateral ones large, 

 irregular. 



IT. SUB-ORDER. AIOLOBRAKCHS (Aiolobranchiata). 



Gills superficial, generally in the form of fusiform 

 processes, plaits, or branching vessels. 



4. FAMILY. Tritonias (Dendronotidae). Tongue 



broad ; teeth many in each cross series ; jaws 

 horny ; tentacles sheathed ; gills fusiform or 

 branched, on each side of back ; vent lateral. 



5. FAMILY. Antiopas (Proctonotidse). Tongue 



broad, teeth many in each cross series 

 jaws horny; tentacles simple, linear, not 

 sheathed ; gills fusiform, on sides of back ; 

 vent dorsal. 



6. FAMILY. Pleurophyllidians (Pleurophyllidiidse). 



Tongue broad ; teeth many in each cross 

 series ; jaws horny ; tentacles simple, united, 

 expanded ; gills in folds, on under side of 

 mantle-margin, which is bent up. 



7. FAMILY. Dotos (Dotomdse). Tongue narrow ; 



teeth in a single central series ; tentacles 

 sheathed at base, retractile ; gills fusiform, 

 on sides of back. 



8. FAMILY. Eolids (Eolididse). Tongue narrow; 



teeth in a single central series ; tentacles 

 subulate, simple, rarely ringed ; contractile ; 

 gills fusiform or branched, on sides of back ; 

 jaws horny. 



9. FAMILY. Hermceas (HermseidaB). Tongue nar- 



