24 



VIVIPARA. 



Fi2. 37. 



separate points of the country, and contains two hundred and 

 two specimens selected from a quantity laid aside as duplicates. 

 The number examined from other sources is certainly equal to 

 this. I now proceed to treat at length each of what I consider 

 synonyms. 



Pal. Integra, Say, as seen from the description furnished below, 

 is distinguished from the typical decisa by having a perfect apex. 

 I do not find this character constant, i. e., in many lots from the 

 same locality I can detect some with a perfect apex, though the 

 majority are truncated. In the Delaware at Burlington, however, 

 it is not rare to find a perfect specimen. I notice quite a differ- 

 ence in the amount of erosion of this and other species, dependent 

 on locality. Thus, I find 3Ielania virginica with the apex alone 

 eroded within only one hundred yards of another locality, where 

 almost every individual has every whirl so much eroded that it is 

 difScult to find any of the outer surface to examine. In addition 

 to this fact of the amount of erosion of some truncated species 

 being somewhat dependent on locality, is the 

 fact of other species being found sometimes 

 eroded and in other places never so, and 

 yet no one would presume to found on this 

 circumstance specific distinction. For ex- 

 ample, Viv. subcarinata, though always 

 truncated in the Delaware, is found in some 

 western localities with a beautifully defined 

 apex, (see figure under that species). Viv. 

 jyondei'osa also, though generally perfect, is 

 found in some of the Alabama rivers con- 

 stantly decollate. It seems to me, therefore, 

 that we must found the specific characters, 

 if existing, on other points than the erosion 

 of the apex, I have not been able to find such. The same 

 sculpturing is present in each form ; the same tendency to varia- 

 tion in outline, &c. I give the original description of Pal. In- 

 tegra below, and a figure (38) of a specimen deposited by Mr. 

 Say in the collection of the Philadelphia Academy of Natural 

 Sciences. The dimensions given by Say are supposed by Halde- 

 man to be a typographical error. 



Paludina Integra, Say. — Shell olivaceous, pale, conic ; whirls six, wrin- 

 kled across ; spire rather elongated, entire at the apex ; suture profoundly 



Vivipara decisa, 

 deformed. 



