142 MANUAL OF NATUBAL HISTORY. 



row ; teeth in a single series ; tentacles none, 

 rudimentary or folded ; gills on side of back ; 

 vent dorsal or sub-lateral ; jaws none. 



10. Family. — Elysias (Elysiidse). Tongue narrow, 



teeth in a single series ; tentacles subulate 

 or linear ; gills in the form of plaits or vessels 

 radiating on surface of back. 



11. Family.— Sea-Slugs (Limapontiidse). Tongue 



narrow ; teeth in a single series ; tentacles 

 none or simple, contractile ; body depressed ; 

 gills none external. 



12 Family. — Oceanic - Slugs (Phyllirrhoidse). 

 Tongue narrow ; teeth in a single series ; 

 jaws horny; tentacles elongate, subulate, 

 simple ; body compressed vertically ; gills 

 none external. 



13. Family. — Phyllidioms (Phyllidiidse). Tongue 

 and jaws none ; tentacles dorsal, anterior, 

 retractile ; labial palpi close, conical, small ; 

 gills in form of radiating folds, on under side 

 of mantle-margin ; vent medial, posterior. 



III. S UB-CLASS. — Heteropodous-Gasteropods 

 (Heteropoda). 



Gills tufted, on inner edge of front of mantle ; 

 foot various, modified and compressed for swimming. 



1. Family — Carinarias (Pterotracheidse). Body 



elongated, gelatinous ; eyes large, sessile ; 

 gills in a small sac, naked, or covered with 

 a thin sub-spiral shell ; operculum none. 



2. Family. — Sea-Arroivs (Sagittidae). Head w'+h« 



