588 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



comparison, especially as they seem to come from quite different horizons. 

 The principal differences observed are the much more obscure, or nearly 

 obsolete, revolving striae, and apparently imperforate axis, of the form here 

 under consideration. 



Locality and jiosition. — Mouth of Judith River, Montana^ from the 

 Judith River beds ; probably of latest Cretaceous age. 



Campeloma multistriata, M. & H. 



Plate 43, figs. 15, a, b, c, d, e. 



Melanin multistriata, Meek and Hayden (1856), Proceed. Acad. Nat. Sci. Philad., VIII, 124. 

 Limnasal multistriata, Meek and Hayden (1860), ib., XII, 431. 



Campeloma multistriata, Meek (1866), in Conrad's Smithsonian Check-List N. Am. Eocene Invertebrate 

 Fossils, 12. 



Fl s- 80 - Shell small, moderately solid, narrovv-subovate; 



spire much elevated, pointed at the apex, which is not 

 eroded ; volutions six and a half to seven, rounded- 

 convex, increasing rather gradually in size; suture 

 campeloma multistriata. deep ; surface apparently smooth, but when examined 



Showing aperture, &c. , , , , i i , n • , i- 



(natural size of one of the under a le » s seen to be marked by very faint lines ot 

 largest specimens), more growth, crossed by numerous obscure, very minute 



clearly than the figure on ' 



plate 43. revolving striae; aperture narrow-subovate, angular 



behind, produced and very narrowly round or subangular and faintly sinuous 

 iu front, usually about equaling the length of the spire; inner lip not thick- 

 ened ; margin of outer lip slightly prominent below, and faintly contracted 

 above. 



Length of a medium-sized specimen, 0.45 inch ; breadth, 0.25 inch ; 

 apical angle, nearly regular, divergence varying with age, usually about 48°. 



I have long been much puzzled in regard to the generic relations of this 

 species, which, so far as can readily be determined from the shell alone, 

 would seem to present characters almost intermediate between several 

 groups. In first indicating it from imperfect specimens, its similarity in some 

 respects to certain American forms of Melamidce, at that time generally 

 referred to Melania, caused its reference to that genus. Subsequent exam- 

 inations of better examples clearly showed that it could not be a true Me- 

 lania ; and although far from being convinced that it is a Limncea, we placed 

 it provisionally, with a query, under that name.* It differs, however, from 



* It was only referred provisionally to the genus Limncea on the supposition that it might pos- 

 sibly be related to L. humilis of the Lymnopkysa group. 



