586 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



that it was founded on one of our western fresh-water shells — to doubt that 

 his type was a reversed specimen of C. ponderosa or C. decisa. Even the 

 etymology of the name Campeloma seems to confirm the conclusion that he 

 had before him a species of this genus, one of the most marked character- 

 istics of which is the waved or sigmoid outline of the margin of its outer lip. 

 After it was found necessary to separate this genus from Viviparity, 

 Bowdich's name Melantho has been generally used for it; but as Bowdieh 

 plainly states that the type of his genus is a marine shell, and does not even 

 hint that it is an American species, there appears to be no reason for apply- 

 ing his name to this genus. 



Campeloma m u 1 1 i 1 i n e a t a , M. & H. 



Plate 44, tigs. 1, a, b. 



Paludina muliilineata, Meek and Hayden (1856), Proceed. Acad. Nat. Sci. Philad., VIII, 120. 



Viripara multilineata, Meek and Hayden (1860), ib., XII, 85. 



Vivipara Nebrascensis, Meek and Hayden (1860), ib., 430. • 



Melantho mnltilineatiis, Meek (1863), in Professor Gill's paper on the Fiviparidw, Proceed. Acad. Nat. Sci. 



Philad., XV, 7. 

 Campeloma multilineata, Meek (1866), in Conrad's .Smithsonian Eocene List, 12. 



Shell subovate ; spire moderate ; volutions six, convex, increasing grad- 

 ually in size, last one rather large and rounded ; suture deep ; surface marked 

 by fine obscure lines of growth, and numerous stronger revolving thread-like 

 stria?; aperture comparatively small, obliquely ovate; inner lip thin and 

 reflexed below, so as nearly to cover the small, deep, umbilical perforation. 



Length, 1 inch ; breadth, 0.64 inch ; apical angle convex, divergence 

 about 55°. 



In some of the specimens, the lower whorl shows faint traces of an 

 obscure revolving ridge just below the suture; this, however, is not a con- 

 stant character, many of the specimens being entirely without any indica- 

 tions of it. On the upper part of the volutions, the revolving lines are gen- 

 erally separated by spaces greater than their own breadth, but they diminish 

 in size, and become more crowded below, excepting near the umbilicus, 

 where they are larger and more distant. Immediately below the suture, 

 there is usually a narrow space, on which the revolving striae are not defined. 



This and the following species or variety are the only forms yet seen 

 from the Upper Missouri rocks that seem certainly to fall into the genus 

 Campeloma. They are not so ponderous as the larger living examples 

 of this group, but still evidently belong to it, as they possess the peculiar 



