340 Remarks on Certain Species of * 



"Remarks : I am indebted to Dr. Mitchell for this shell, which was 

 sent to him by a friend from Ohio. It is rather larger than the IT. 

 clausa Say, and H. jejuna Say, but in form resembles them. It may be 

 distinguished from the latter in not being perforate, and from the former 

 in having a sharper lip. In its stria) it is distinct from both, in having 

 them larger and much better defined. 



" Hab. Ohio. Diam. 7. Length .4 of an inch." 



Lea's description agrees fairly with the shell now known in 

 our cabinets as II. Mitchelliana. 



Looking at his " Remarks," however, I cannot wonder at the 

 many doubts which have arisen as to the shell intended to be 

 indicated, inasmuch as the comparison with H. clausa and H. 

 jejuna scarcely admits of satisfactory explanation. 



The fact is, that Lea misapprehended both species, as I learn 

 from correspondence with him, — he had in his cabinet under the 

 latter name, a small form of II. clausa, and I have reason to 

 believe that a variety, with imperfectly developed lip, of the 

 very shell which he was about to describe as II. Mitch- 

 elliana, represented the former species. The language used 

 by Lea shows that he referred to an imperforate shell as H. 

 clausa. 



II. Mitchelliana is certainly very closely allied to H. clausa, 

 especially the form described by Say, but in Lea's species the 

 umbilicus is entirely closed, and at the base the spiral impressed 

 lines are more distinct, in which respect it agrees with II. clausa 

 var. subalbolabris, to which I have already referred. 



In II. clausa the umbilical region is more widely excavated, 

 and the groove, behind the reflected lip, producing the con- 

 traction of the aperture, is continued at the base of the shell, 

 becoming wider as it joins the umbilical opening. In II. Mitch- 

 elliana the groove is almost obliterated at the point of reflection 

 of the lip over the umbilicus, by the more tumid character of 

 the last whorl. 



All the specimens in my cabinet of //. Mitchelliana are from 

 Ohio. 



