984 FRESH-WATER BIOLOGY 



44 (43, 45) Surface smooth or finely striate Section Torquis Dall. 



^■^^ 



This group of small species is o\ general distribution from the At- 

 .7i:*5^ /--^ lantic to the Pacific. Type, Planorbis parvus Say, (Fig. 1433; X 45)- 



Fig. 1433- 



45 (43, 44) Shell minute; surface costate. . . Section Armiger Hartmann. 



A The typical species only, Planorbis crista L., (Fig. 1434; X 7), repre- 



sents this group in our fauna and has been recorded from Maine to Illi- 

 nois and northward. 



Fig. 1434- 



46 (34) Aperture with one or more sets of laminae or teeth behind the margin. 



Segmentina Fleming. 



The typical Segmentinae are not represented in our fauna. All of the 

 American species belong to the subgenus Planorbula Haldeman. The type 

 5. armiger a Say, (Fig. 1435; X 2) is common in the northern Eastern States 

 and Canada. 



Fig. 1435. 



47 (33) Shell spiral, dextral, flattened above and convex below; body-whorl 



very large Subfamily Pompholiginae . . 48 



48 (49) Shell imperforate Pompholyx Lea. 



'i| \ Two or three species only are known from California. Type, P. effusa 



•)) Lea., (Fig. 1436; X 2i). 



Fig. 1436. 



49 (48) Shell deeply umbilicate Carinifex W. G. Binney. 



A\' \\l// ) '^^^ typical species, C. newberryi Lea., (Fig. 1437)1 is. from Cali- 



\V^ijjg; / fomia. 



Fig. 1437. 



50 (53) Shell spiral, sinistral. Animal sinistral; tentacles slender, cylindrical. 



Family Physidae . . 51 



