WHITEAVES.] LARAMIE AND CRETACEOUS IN'YERTEBRATA. 17 



AcROLOXrs RADIATCLUS. (X. Sp.) 



Plate 3, figs. 1 Ji la. 



Shell cleprc^^ed conical, very slightly elevated, the height heing 

 about one-fourth the maximum breadth . apex eccentric, inclined dis- 

 tinctlv to the left and placed about half way between the centre and 

 the piosterior end : ba^e. or margin of aperture, ovate in outline, not 

 ■quite one-third longer than broad, rounded in front and somewhat 

 pointed behind. 



Surface marked by minute concentric lines of growth, which are 

 crossed by numerous, closely disposed and almost equally minute 

 radiating raided lines, both of which are too small to be seen without 

 the u-e of a lens. 



Length of the only specimen collected, five millimetres and a half: 

 maximum breadth, four mm. : ajjproximate height, from apex to base, 

 about one mm. 



Mouth of Blind Man Eiver, Township 30. Eange 27, west of 4th 

 Principal Meridian, J. B. Tyrrell, 1834. From the same geological 

 horizon and from the same beds as Limncea tenuicostata. 



AcROLOxrs MixcTL's, Meek and Hayden. 



JVktia miniifa, Meek and Hayden. 18.50. Proc. Ac. Xat. Sc. Phil., p. 120. 



Ancylus [Acroloxi'si mirmtii?, 31. & K. ISiiO. Ho., p- 432. 



^-icroloxus minulus, Meek. 1S76. Eep. U.S. Geol. Surv. Terr., vol. IX., p. .51.3 



pi. 44, fig. 10. Illustrated also in Dr. AVhite's Eev. 



Xon- Marine Foss. Moll. X. Am., pi. 24, fig. 27. 



North or Second Branch of the Milk Eiver, CI. M. Dawson, 1874, 

 H. M. Xorth American Boundary Commission. Gooseberry Caiion, St. 

 Mary Eiver, and Old Man Eiver, two miles above Eye-G-rass flat, 

 <J. M. Dawson, 1881. Pincher Creek, T. C. Weston, 1S8.3. One or two 

 specimens from each locality. All from the St. Mary E. Serie.^. 



The identification of these little shells with the species named above 

 is not altogether satisfactory, first, on account of the vagueness of Mr. 

 Meeks definition of the characters of: A. minnfus, and secondly, because 

 of his statement that the specimens from the upper Missouri country, 

 decribed under that [name '■' may possibly belong to more than one 

 .species.'^ Some of them may perhaps be referable to A. radiatulus. 



July, 1885. ^ 



