GASTEROPODA. 171 



Shell spiral, more or less elongated, thin, translucent ; body-whirl large, 

 aperture rounded in fi'ont ; columella obliquely twisted. 



Animal with a short, broad head ; tentacles triangular, compressed ; lin- 

 gual teeth {L. stagnalis) 55.1.55, about 110 rows, central teeth minute, 

 laterals bicuspid, the inner cusp largest. Z. peregra feeds on the green fresh- 

 water algae; L. stdgnalis prefers animal substances. 



Bisir. 50 sp. Europe, Madeira, India, China, N. America. 



Fossil, 70 sp. Wealden — . Brit. Trance. 



Sub-genus, Amphij)eplea, Nilsson. A. glutinosa, PI XII. fig. 31. Shell 

 globular, hyaline. Animal with a lobed mantle, capable of expansion over 

 the shell. Europe ; Philippines. 



Fig. 96. 

 Chilinia, Gra/. Chilian-snail. 

 Ex. C. pulchra, D'Orb. fig. 96. Sijn. Dombeya, D'Orb. 

 Shell oval, thin, ornamented with dark spots or wavy bands ; columella 

 thickened, with 1 or 2 strong prominent folds. 



lyistr. 14 sp. S. America; in clear running streams. 

 Fossil, 1 sp. Miocene, Rio Negro, Patagonia (D'Orb.) 



Physa, Draparnaud. 



Tyj)e, P. fontinaHs, PL XII. fig. 32. Etgm. Physa, a pouch. 



Syn. Bulin, Adans. Eivicola, Eitz. Isidora, Ehr. 



Shell ovate, sinistrally spiral, thin, polished ; aperture rounded in front. 



Animal with long slender tentacles ; the eyes at their bases ; mantle 

 mai'gin expanded and fringed with long filaments. 



P. hypnorum (Aplexa, Fleming) has an elongated spire, and the mantle 

 margin is plain. Physopsis, Krauss, S. Africa, has the base of the colu- 

 mella truncated. Caviptoceras (terebra), Benson, India, has the whirls dis- 

 united, and the peristome continuous. Zf'-CS^ 



Bistr. 20 sp. N. America, Europe, S. Africa, India, Philippines. • 



Fossil, 14 sp. Wealden — . Brit. France. The lai-gest living sp. (P. 

 Maugerse, California) is 15 lines in length. A fossil sp. found at Grignou 

 measures 26 lines, and another equally lai'ge occurs in ludia. 



Ancylus, Geofi'roy. River-limpet. 

 Etym. Ancylus (agkulos) a small round shield. 



