INVERTEBRATE PALAEONTOLOGY. 587 



form of aperture, with its produced narrow base, and the same sigmoid 

 outer lip seen in the characteristic living species. 



Among our existing American species, this shell may be compared with 

 C. decim, Say, C. regularis, Lea, and C. lima, Anthony. It will be easily 

 distinguished from them all, however, by its revolving lines and small, deep 

 umbilical perforation. 



At the time we proposed to change the name of this species to V. Nebra- 

 censis, we were under the impression that the name multilineatd would have 

 to be retained for a recent species described by Say. As conchologists, 

 however, have decided that the form to which he applied that name is most 

 probably an introduced variety of V. Benga/etisis, and the Campeloma 

 (— Melantho) group is also now regarded as a distinct genus, the original 

 name multilineata is here restored. 



Locality and position. — Fort Clarke, Dakota, on the Missouri; from the 

 Fort Union group (probably Eocene). 



< a m i> «■ i » in ■•> v e t n I a , M. & H. 



Plate 44, tigs. 14, a, b. 



Pallidum vetula, Meek and Hayden (1850), Proceed. Acad. Nat. Sci. Philad., VIII, 121. 



Vivipara vetula, Meek and Hayden (18(50), ib., XII, 430. 



Melantho vetulus, Meek (1803), in Professor Gill's paper on the Vimparidai, Proceed. Acad. Nat. Sci. 



Philad., XV, 7. 

 Campeloma vetula, Meek (1800), in Conrad's Smithsonian Eocene List, 12. 



Shell of medium size, conoid-ovate, rather thin; spire moderate; volu- 

 tions about five and a half, moderately convex, increasing rather gradually in 

 size from the apex, last one somewhat ventricose ; suture deep, and only 

 slightly oblique ; surface marked by fine, indistinct lines of growth, some- 

 times crossed by nearly obsolete revolving striae ; umbilical region indented, 

 but scarcely perforated ; aperture ovate, equaling generally a little less than 

 half the entire length. 



Length, 0.88 inch ; breadth, 0.60 inch ; length of aperture, 0.47 inch ; 

 breadth of same, 0.37 inch. 



This shell varies to some extent in form ; the smaller individuals having 

 the spire proportionally less ejevated and the body-volution more ventricose. 

 I have long been nearly satisfied that it is only a variety of the last; but 

 having already separated it under another name, it is perhaps better to con- 

 tinue this arrangement until we can have more extensive collections for 



