104 LAND AND FRESH-WATER SHELLS Or N. A. [PART IL 



Oregon. T. Nuttall collected a single specimen. 



" Differs from PL trivolvis, Say, in the acuteuess of the ribs, and in their 

 being more distant." Cuming MS. (^Carpenter.) 



Planorbis subcrenatus, Carpenter, Proc. Zool. Soc. 185G, p. 220. 



The above is the original description of Mr. Carpenter. The 

 specimen from which it was drawn is figured in mj Fig. ITG. 

 It has been found in Washoe (Neiccovib). 



Planorbis lentlts, Say. — Shell dull brownish or yellowish-brown, 

 sub-carinate above, particularly in the young shell ; whirls nearly five, 

 striate across with fine raised, subequidlstant lines, 

 Fig. 177. forming grooves between them ; spire concave ; aper- 



ture large, embracing a large portion of the penulti- 

 mate volution ; labrum more acutely but not very 

 prominently arcuated above, its basal portion hori- 

 zontally subrectilinear, in the adult, and not ex- 

 tending below the level of the base. 



I obtained this species in the canal at New Orleans, 



and am indebted to Mr. Maclure, and also to Mr. 



Barabino, for many fine specimens collected in the 



vicinity of that city. I also found the same species 



at Ojo de Agua, Mexico, when travelling in that 



country with Mr. Maclure. It differs from the P. 



Planorbis lentus. trivolvis in having the labrum less prominent above, 



and the basal portion of this part being in the adult 



horizontally subrectilinear, so as not to touch a plane on which the base 



of the shell may rest ; the aperture also is more transverse. {Say.) 



Planorbis lentus, Sat, Am. Conch, pt. 6, pi. iv, f. 1 (1834) : Binney's ed. 

 210, pi. iv, f. 1,— Haldeman, Mon. 18, pi. iii, f. 4-6 (1844).— De- 

 Kay, N. Y. Moll. 60, pi. V, f. SO*, a, b (1843).— Axon. Can. Nat. II, 

 203 fig. (1857) (not Old. z=fullax). 



Fig. 177 is a fac-simile of that of Mr. Say, whose description 

 •also is given above. 



It is said to have been found at several points between Xew 

 Braunfels, Texas, and South Carolina, and in New York. 



Prof. Adams refers the species to PI. corpulentus in the List 

 of Middlebury Shells, to trivolvis in the Shells of Vermont. 



Gould's description and figure of PL lentus is referred by 

 Haldeman to PL fallax. 



