ROSTRIFERA. 15 



gate, subulate, implanted in the fleshy pro- 

 boscis. Carnivorous, venomous, marine. 



II. PROBOSCIDIFERA. Head small; proboscis 

 retractile under the base of the tentacles; 

 teeth variable, in three, five, or one longitu- 

 dinal series, on an elongated cartilaginous 

 tongue membrane. Carnivorous, marine. 



III. ROSTRIFERA. Head produced into a ros- 

 trum, with the tentacles on the side of its 

 base ; teeth in seven longitudinal series, on a 

 cartilaginous tongue membrane. Phytopha- 

 gous, marine, fluviatile, and terrestrial. 



The two first sub-orders are confined to marine 

 animals ; the last contains a few fluviatile or terres- 

 trial species. 



Sub-order III. ROSTRIFERA. 



Head moderate, with a more or less elongated, 

 produced, contractile, transversely-annulated ros- 

 trum ; tentacles subulate, far apart, on the sides of 

 the base of the rostrum ; eyes on the outer side, or 

 behind the base of the tentacles ; teeth on an elon- 

 gated linear lingual membrane partially received in 

 the visceral cavity, in seven, longitudinal series ; the 

 central and inner lateral teeth fixed, with a broad 

 base ; the two outer lateral teeth versatile, suberect, 

 the upper edge lobed. Phytophagous, marine, flu- 

 viatile, and terrestrial. 



This group is divided into sections, according 

 to tfre form of the foot, which is modified by the 



