wHiTEAVES.] LARAMIE AND CRETACEOUS INVERTEBRATA, TS 



maximum breadth of the same, as measured across the centre of the 

 body-whorl, ten mm. length or height of body-whorl, not c|uite nine 

 mm. 



Belly Eiver, two miles above Woodpecker Island, — and Beilj? Eiver, 

 east side of Driftwood Bend, G-. ^L Dawson, l-si. Snuth Saskatche- 

 wan, one mile abuve the mouth of the Bow Eiver, T. C. Weston, 1883. 

 Appaventlj' not unfrequent at each of these localities. 



The description given abuve and the tigure on plate 10 are both 

 taken from an unusually perfect and well preserved specimen collected 

 by Mr. Weston on the South Saskatchewan. In Mr. Meek's diagnosis 

 of the characters of G. subtortunsa the number of volutions is said to be 

 "about five" and his measurements and figures of that shell do not 

 cori-esjjond at all well with the pi-oportions and contour of the Cana- 

 dian specimens. Dr. C. A. White, however, who has kindly compared 

 the fossil obtained by Mi-. Weston with the specimen described and 

 figured by Meek, informs the writer that the former is " without doubt 

 the G. (?) subtortuosa of Meek and Haj-den," and adds that Meek's 

 type of that species is "imperfect and partially crushed," and that it 

 would not warrant a definite determination of the number of whorls. 



The only species with which the present shell is at all likely to be 

 confounded is the Cassiopella turricnla of White, but the latter is stated 

 to have nine or ten volutions, its base Js said to be distinctly umbilicated, 

 and the spiral keel which encircles its sjaire is represented as placed 

 considerably below the middle of each whorl. 



It is difficult to see how G. subtortuosa can be separated generically 

 from such living species as the G. arutocarinata of Lea and other forms 

 belonging to that section of the genus. 



IItdrobia subcylindracea. (N. Sp.) 

 Plate 10, fig. s. 



Shell very small, narrowly cUiptic-subovate, rather slender, the length 

 being about one-third greater than the maximum breadth : volutions 

 five, those of the spire very gently convex, their sides being compressed 

 somewhat obliquely ; last whorl of the spire nearly or quite equal to 

 the body whorl in breadth or convexity : suture distinct : spire about 

 twice as long as the aperture and rather obtuse at its immediate apex. 

 Body-whorl comparatively narrow, subcylindrical above and imperfor- 

 ate at the base: aperture obliquely subovate, somewhat iwinted above: 

 outer lij) simple and rather thin. 



Surface smooth and polished. 



