INVERTEBRATE PALEONTOLOGY. 579 



apex of its spin- much more obtuse.* It also has generally about one whorl 

 less, and its body-volution is usually more compressed above just below the 

 suture, and less regularly rounded, or more nearly subangular below the 

 middle, while its columella differs in being imperforated, and its lines of 

 growth are stronger and more oblique. 



It is also somewhat analogous to P. Desnoyesii, Deshayes (Coq. Foss., 

 II, pi. 15, figs. 7-8), but its spire is more depressed, and its aperture more 

 angular above, where its inner lip does not present the peculiar thickening 

 characteristic of that species. It also differs in the imperforate and more 

 deeply arcuate character of its columella, as well as in the obscurely sub- 

 angulated character of its body-whorl. I am not acquainted with any nearly 

 allied recent species. 



Locality and position. — Same as last. 



Viviparus Conradi, M & H 



Plate 42, figs. 15, o, b, c, d. 



Paludina Conradi, Meek and Haydeu (1856), Proceed. Acad. Nat. Sci. Philad., VIII, 122. 



Fivipara Conradi, Meek and Hayden (I860), XII, 185. 



Viviparus Conradi, Meek and Hayden (1863), in Professor Gill's paper on the Family T~ivipaHda>, 6. 



Shell conoid-subtrochiform ; spire distinctly conical, of medium height, 

 pointed at the apex ; volutions six, flattened on a line with the slope of the 

 • spire, last one more or less distinctly angular a little below the middle; 

 suture linear; surface marked by fine obscure lines of growth; aperture 

 varying from subquadrate to subcircular ; columella deeply arcuate, not per- 

 forated. 



Length, 1 inch; breadth, 0.66 inch; length of aperture, 0.45 inch; 

 breadth of same, 0.33 inch. 



In young specimens, the angle on the lower outer part of the body- 

 whorl is very strongly defined, and imparts a subquadrate form to the aper- 

 ture ; but as the shell advanced in size, the angle became less distinct, and 

 the aperture more rounded. Some of the specimens show apparently very 

 obscure traces of fine revolving stria? ; but I am not sure that these are 

 really surface-markings. 



This species is quite distinct from all those yet known in these for- 

 mations, though more nearly related to our V. trochiformis than to any of the 

 others. It will be readily distinguished from that shell, how ever, by its more 



* This character is not very well expressed in onr figures on plate 44. 



