396 PROCEEDINGS OF THE ACADEMY OP 



ence between the form described by Defrance as 23. vertebralis, and Dr. Mor- 

 ton's B. asper (or B. Spillmannii Con.), still there is no character by means of 

 which we can satisfactorily separate them. PI. iii. fi.cr. 2 is from the European 

 form ; figure 3 is from a young individual of Morton's carinatus, which is the 

 same as the variety figured by d'Orbigny ; figure 4 is from one of Morton's 

 original specimens of B. asper, which is characterized by a broad dorsum and 

 large triangular nodes. B. Spillmannii Con. is a distinct link between the 

 variety asper and the undulated form ; the nodes on Mr. Conrad's specimen 

 of that species being elongated into prominent crescents. Between that and 

 the rougher forms of Morton's carinatus, (the typical variety of B. anceps), it 

 is impossible to draw a dividing line. Again, some of Dr. Morton's speci- 

 mens of this last named species are perfectly smooth, while others are so 

 rough that when I thought that distinct from B. asper, I did not know to 

 which species to refer them. Mr. Conrad's Tippaensis is the typical form of 

 B- carinatus of Morton. 



We have now but one other form left, and to ascertain positively its rela- 

 tions, will require a larger series of specimens than I have yet seen. I refer 

 to B. cohimna Morton, Syn., p. 4-1, pi. 19, fig. S. This species was described 

 by Dr. Morton from half a dozen fragments of about an inch in length. I have 

 been unable to discover any trace of a septum in any of them. They are 

 elliptical to ovate, and marked rounded, sinuous ribs which cross the dorsum, 

 pass downwards at a slight angle to about the middle of the side where they 

 curve and then run transversely around the ventrum. The angle at which 

 these ribs bend upwards from the middle to the dorsum is not more than half 

 as much as in the preceding species, but in one or two specimens I have detect- 

 ed another series of lines which may be lines of growth, and which would 

 give the mouth much the shape of that in B. anceps. Dr. Morton's illustra- 

 tion of this form is almost utterly worthless. He represents the ribs separated 

 at too great distance, and much too distinct. This direction is also incorrect ; 

 they should bend twice as abruptly from the middle toward the widest end, 

 on the side nearest the figure of Rostellaria pennata, which is the dorsal side, 

 and should be less distinct towards the ventrum, since on that side they are 

 sometimes almost obliterated. It is by no means improbable that this is 

 merely the young of one of the many varieties of B. anceps. It is certainly 

 not a Hamite as d'Orbigny suggested in his Prodrome de Paluontologie Strati- 

 graphique. 



On the Mollusca of Harper's Ferry, Virginia. 



BY GEORGE VV. TRYON, JR. 



In the month of June, 1859, I was called by business to Harper's Ferry, and 

 while there, having a very brief period of leisure at my disposal, I employed 

 it in making a collection of the shells of the vicinity. I was struck at the 

 time with the exceeding abundance of these, both in individuals and species, 

 and also by the prevalence of certain external characters, much more promi- 

 nently marked, than in the same shells from the vicinity of Philadelphia. 

 These peculiarities, on a recent re-inspection of the shells, have appeared to 

 me worthy of mention ; and the subject of geographical distribution may re- 

 ceive some new light from the publication of a list of the Mollusc3 of the 

 mountainous region of Virginia. The species collected are as follows : 



GASTEROPODA. 



Melaniad.e. 



These shells were numerous upon the rocks in the bed of the Potomac, just 

 below the junction of the Shenandoah River, and at the U. S. Rifle Armory 

 on the latter stream. 



[Dec. 



