INVERTEBRATE PALAEONTOLOGY. 581 



flattened, each having around the middle two small revolving ridges; last one, 

 especially in young and medium-sized specimens, distinctly angular below the 

 two revolving ridges; suture distinct, but generally not very deeply im- 

 pressed; surface marked by rather fine lines of growth, which are crossed 

 by exceedingly delicate, obscure, revolving hair-lines; aperture broad rhom- 

 bic-ovate, or subcircular, very slightly oblique ; inner lip rather thin, a little 

 reflected upon the deeply arcuate columella, so as nearly, or sometimes quite 

 to close the very small, oblique, umbilical pit. 



Length, 1.20 inches ; breadth, 0.90 inch ; length of aperture, 0.52 inch ; 

 breadth of same, 0.46 inch; apical angle convex, divergence about 67°. 



The two revolving ridges mentioned on the middle of the whorls, 

 although moderately distinct, are not sharply elevated, and generally become 

 nearly or quite obsolete near the summit of the spire and on the body-whorl 

 of large specimens. They are usually about equidistant from each other, 

 and from the suture above and below; sometimes a third smaller ridge is 

 developed near one of the others. The fine revolving hair-lines are scarcely 

 visible without the aid of a lens, and often become obsolete on the lower 

 whorls. The angle around the middle of the body-whorl is always well 

 defined; but it is never exposed on the volutions of the spire, because the 

 upper edge of each turn abuts directly against it on the succeeding one 

 above. 



Like some others of our Lignite fossils, this species far more nearly 

 resembles certain Oriental forms than any of our existing North American 

 species. Probably its nearest existing representative is V. Bengalensis of 

 Lamarck, some of the angular varieties of which it closely simulates. It 

 differs, however, in having its whorls more flattened, its spire more depressed, 

 and its body-volution proportionally broader and more constantly angular 

 around the middle. I have before me, from the surface-loam near Hevey- 

 leyhein, China, some specimens sent to the Smithsonian Institution by Pro- 

 fessor Pumpelly, marked Paludina lineata, Valenciennes (a variety, I believe, 

 of V. Bengalensis), some of the younger of which strikingly resemble the 

 form under consideration. They are all, however, more particularly the adult 

 examples, more slender, with a more produced spire, and more convex as well 

 as more rounded volutions. 



It will be at once distinguished from all of the other known Upper 

 Missouri species by ils very obvious differences of form and other characters. 



