64 SYSTEMATIC ARRANGEMENT 



Suborder III. Rostrifera, Gray. 



Head moderate, with a more or less elongated, produced, contractile, 

 transversely annulated rostrum. 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 elongated, linear, lin- 

 gual membrane, partly received in the visceral cavity, in seven series, 

 3 • 1 • 3 ; the central and inner lateral fixed, with a broad base ; the 

 two outer lateral versatile, suberect ; the upper edge lobed. 



Phytophagous. 



I. Platypoda. Foot depressed, expanded : for crawling. 



a. Eyes pedicelled. 



b. Eyes sessile, basal, exterior. 



c. Eyes sessile, basal, interior and posterior. 



II. Protopoda. Foot roundish, truncate or clavate. 



III. Leptopoda. Foot compressed : for leaping. 



a. Eyes pedicelled. 



b. Eyes sessile. 



IV. Heteropoda. Foot compressed, fin-like, with a small sucker. 



I. Platypoda, Gray. 

 Foot depressed, expanded : for crawling. 



I. Podophthalma. Eyes on the top of cylindrical peduncles, 

 separate from and at the outer side of the base of the elonyate 

 subulate tentacles. 



Fam. I. AMPULLARIAD^. 



Rostrum produced, divided into two elongated subulate lobes. 

 Tentacles filiform. Eyes peduncled. Gill one, rudimentary. 

 Mantle with a large pulmonary sac on each side. Foot and opercular 

 mantle simple. Operculum annular, regular. Mantle with a more 

 or less elongate siphon in front. Male organ on the edge of the 

 mantle. 



Shell subglobose. Periostraca hard, polished, olive. Mouth entire. 

 Peristome continuous. 



Fluviatile. Oviparous. Eggs globular, deposited in masses on 

 plants, &c. 



The length of the peduncle of the eye in Ampullaria varies in 

 different species ; in some it is well marked ; in others the eye 

 appears to be only placed on a small tubercle at the base of the ten- 

 tacles. 



The Ampullaritz live chiefly in marshes which are subject to inun- 

 dation ; they are never found in rapid running streams. They are 

 generally abundant, and cover a large space of country. They live 



