WHiTEAVEs.] LARAMIE AND CRETACEOUS INVERTEBRATA. 71 



Planorbis paucivolvis. (N. Sp.) 

 Plate 10, fig. .-,. 



Shell very small, discoidal, thin, nearly flat or slightly concave on 

 one side and apparently somewhat more convex near the circumfer- 

 ence and dejDressed in the centre on the other. Volutions four, slendci- 

 and increasing very slowly in size, their dorso-ventral diameter being 

 not much greater than their breadth from side to side, — cluscly coilcil 

 but not very deeply embracing, so that the greater j^art of all the inner 

 whorls is exposed to view, at any rate on the left or flattened side. Body 

 whorl angnlated at the junction of its left or flattened side with the 

 periphery. 



Surface markings unknown, the outer layer of the test being exfolia- 

 ted in the only jjerfect specimen collected. 



Maximum diameter of the largest specimen, about two millimeties 

 and a half: greatest breadth of the same, ajiproximately, three-quartcj-s 

 of a millimetre. 



Belly Eivor, near its junction with the Bow Eiver, G. iM. Dawson, 

 1881 : two small and very badly preserved specimens. South Saskat- 

 chewan, six miles below the mouth of Bow Eiver and thirty-five teet 

 above the water level, (1. il. Dawson, 1881 : one apparently adult and 

 nearly pertect specimen and a smaller one. 



The only perfect and tolerably well preserved example of this shell 

 that has yet been obtained has most of the right side buried in the 

 matrix. 



Phtsa Copei, White. 



Phijm Cop,:i, White. 1877. Bui. U. S. Geol. Surv. Terr., vol. III., p. 602. 



" " ISSO. U.S. Geol. Surv. Terr., Contr. to Pal., Nos. 2-S, p. s.i, 



pi. 24, figs. 4a and b. 

 " " 1SS3. Rev. Non-Marine Foss. jMoII. N. Am., pp. 43, 44, pi. 



2-5, figs. 1 and 2. 



Belly Eiver, near its junction with the Bow Eiver, G. M. Dawson, 

 1881: one very small specimen. South Saskatchewan, six miles belnw 

 the mouth of the Bow Eiver ami thirty-five feet above the water level, 

 G. M. Dawson, 1881 : an embryonic example not quite three milli- 

 metres in length. South Saskatchewan, one mile below the mouth of 

 the Bow Eiver, T. 0. Weston, 1883 : a full grown individual, moi'C 

 than an inch and a half long. 



