64 LAND AND FRESH-WATER SHELLS OF N. A. [PART IV. 



Habitat. — Ohio River. 



Length, nearly three-flfths inch; of the aperture, one-fourth inch. 



Observations. — May be readily distinguished from M.Virginica by 

 the much more rapid attenuation of the spire, and in the proportional 

 difference in the length of the aperture, which in the Virr/inica is not 

 more than equal to the length of the second and third whorls. — Say- 



Melania substricta was proposed by Prof. Haldeman instead 

 of conica under the impression that the latter name was pre- 

 occupied. He afterwards used the name for a new species. 



The following species, described by Menke, are all synonymes 

 of canalicidatum : 



3Ielania exarata. — Shell conically turreted, acute; apex eroded; 

 striate, greenish-brown; last whorl encircled by two transverse 

 sulci, plane between ; the other whoi'ls carinate in the middle ; 

 aperture obliquely ovate ; lips alate, arcuate, margined within, 

 extreme margin subreflected. 



Habitat. — Ohio River, at Cincinnati. 



Long., 13 1in. ; lat., 6 Ym. — Menke. 



3Ielania ligata. — Shell turreted, apex eroded, truncate, with trans- 

 verse acute striae, below sulcate, corneous ; whorls seven, convex, 

 the last bifasciate, the others singly banded. 



Habitat. — Ohio River, at Cincinnati. 



Long., lin. ; lat., 3.^ lin. — Mcnke. 



Ilelania auriscalpium. — Shell turreted, apex truncately eroded, 

 smooth, corneous, whorls six, convex, the last doubly banded, the 

 others singly banded ; lip arcuate, sub-alate, produced in front. 



Habitat. — Ohio River, near Cincinnati. 



Long., 10; lat., 3:J lin.— i)/e»le. 



It is questionable whether P. canal iculatum is really distinct 

 from P. nndulatum; indeed, the transition between the 

 smooth and tubercled surface is so gradual, and the range and 

 Fig 123 development of the two species in different localities 

 so exactly similar that I am inclined to think them 

 identical, but like Mr. Lea and Prof. Haldeman, 

 who entertain the same views, I do not feel at 

 liberty to unite them as j^et. 

 As an illustration of the great difficulty attending the deter- 

 mination of species in this family, I figure (fig. 123) a depauper- 

 ate s^pecimQn of canaliculatum furnished me by Prof. Haldeman. 



