1894. PROCEEDINGS OF THE NATIONAL MUSEUM. 135 



This species is represented by only ii single, somewhat imperfect, 

 natural mold of the exterior of the shell, and which does not show the 

 character of the aperture. It is therefore referred to Gouiohasis 

 because of its external form and features. It bears a general resem- 

 blance to G. macilenta White, of the Bear Eiver formation, but it differs 

 in lacking certain of the surface markings of that species. 



GONIOBASIS, doubtful species. 

 Plate VIII, fig. 10. 



Another specimen, evidently referable to Goniobasis, was found asso- 

 ciated with the foregoing. It resembles that species in certain respiicts, 

 but the apical angle is considerably greater and the shell is therefore 

 less slender. It i)ossibly belongs to the same species with the forego- 

 ing, but I am inclined to regard it as representing another form. 



Family M e i. A N 1 1 D .55 . 

 PYRCiULIFERA MEEKIII, new spefues. 

 J'late, VIII, fi.n. r.i. 



The collection contains a single specimen, in the condition of a nat- 

 ural mold, which I have little, if any, doubt represents a species of 

 Pyrgnlifcrti. The form and character of the aperture are not shown, 

 but the surface features agree well with those of typical species of that 

 genus, and they are much like those of some individual varieties of 

 P. humerosa which were found by Mr. T. W. Stanton in western 

 Wyoming. The volutions, however, are more regularly convex, and 

 the revolving lines finer and more numerous than I have found them 

 to be on any specimens of P. Jmmcrosa. I therefore give it a new 

 specific name, selecting that of the founder of the genus. 



The discovery of PyrguMfera in the Dakota formation is of special 

 interest, not only because that genus has not hitherto been found in 

 any other North American formation than the Bear River, but because 

 that formation is believed to be of nearly, if not quite, the same age as 

 the Dakota. 



Family V i V I P A Ri n ^ . 



VIVIPARHS IIICK.SII, newspoeies. 



Plate VIII, fius. 11, 12. 



The collection contains three or four imperfect natural molds of a 

 small species of Viviparus, artificial casts of two of which are figured 

 on plate viii. The species is a little more elongate, and the spire more 

 acute, than is usual with Yiviparus., but a portion of the aperture 

 shown by one of the sj^ecimens indicates that it was like that of typical 

 forms of that genus. 



