540 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



PHYSID^E. 

 Genus BULINUS, 0. F. Miiller. 



Si/uon.— Bulinus, Miiller (1/81), iu Natnrforsch. Stuck., XVI, 1.— Beck (1S37|), Iud., 116 (as a subgenus). — 

 H. aud A. Adams (1855), Genera Recent Moll., II, 25!).— Binney (1865), Land and 

 Fresh-water Shells N. Am., part II, 97. — Tryon (1865), Am. Jour. Conch., 11,9 (as a 

 subgenus under Physa). — Dall (1870), Ann. Lye. Nat. Hist. N. Y., IX, 356 (not Bulinus, 

 Studer, Hartm., and others). 



Aplexa, Fleming (1H28), British An., 276. — Beck (1837), Ind., 116 (as a subgenus). 



Aplexus, Gray (1840), in Tnrton's Man. (2d ed.),255. 



Diastropha (Guild.), Gray (1840), ib., 16. 



Xauta (Leach, MS.), Gray (1852), iu Leach's Synop. Moll. Brit. Mus., 110. 



EUjm. — Vocab. barb. 

 Examp. — B. hppnorum, Linn. 



Shell sinistral, elongate-subovate, and thin; spire produced, acuminate; 

 aperture narrow and more or less produced anteriorly ; inner lip generally 

 nearly or quite simple ; outer lip sharp ; surface polished. 



This genus includes species nearly like some of those of the genus 

 Physa, with which it agrees in the sinistral character and general appearance 

 of the shell, as well as in the habits of the animal — both inhabiting the fresh- 

 water ponds of this country and Europe. The shells of Bulinus, however, 

 are more elongated, and have a more acuminate spire than those of Phym, 

 while the animal of this group differs from that of Physa in having its man- 

 tle-margin simple instead of digitate. Some conchologists, however, only 

 regard these differences as being of subgeneric importance. 



This genus probably dates back to the Wealden epoch, if not to some- 

 what earlier times. We find forms agreeing with it in this country in beds 

 either belonging to the latest Cretaceous or the oldest Tertiary age. Similar 

 species are also found in the Lignite formation at the mouth of the Rhone in 

 France. Some of these, such as Physa Galloprovincialis, P. Gardanensis, 

 and P. Drapernaudii of Matheron, attain quite large sizes. 



Bulinus subelongatus, M & H 



Plate 42, figs. 13, a, b. 



PUijsa subelongata, Meek and Hayden (1856), Proceed. Acad. Nat. Soi. Philad., VIII, 120. 



Physa (Aple.ra) subelongata, Meek and Hayden (I860), ib., 431. 



Aplexa subelongata, Meek ( 1866), in Conrad's Smithsonian Cheek-List N. Am. F.ocene Invert. Fossils, 9. 



Shell rather large, elongate-subovate or subfusiform ; spire elevated, 

 pointed at the apex ; volutions six to six and a half, nearly Hat, suture oblique, 

 linear, and but -slightly impressed; surface smooth, or with very obscure 



