10 LAND AND FRESH-WATER SHELLS OF N. A. [PART lY. 



Habitat. — Tennessee. 



Observations. — Another of the short, heavy forms in this genus, so 

 unlike the normal type of lo spinosa ; we think no one need confound 

 it "With any other species; its short, heavy, flattened spines jutting 

 out like so many miniature spear-heads, and its peculiarly twisted 

 columella will readily characterize it. The columella is also covered 

 with a dense callous deposit, increased in thickness at its upper part 

 and often blotched with dark red at that point ; irregular, ill-defined, 

 but broad bands are seen in the interior, often faintly visible on. the 

 epidermis. Appears to be a rather common species in some localities, 

 of which I possess some hundreds of specimens. — Anthony. 



Dr. Brot considers this, and all the other species of lo iden- 

 tical with I. Jluvialis. 



Mr. Reeve suspects the specific identity of lo hrevis and 

 spirostoma, and I am convinced that the latter is only an aber- 

 ration of growth like 7. gibbosa; it is, however, a very graceful 

 and beautiful shell. 



The follovring is the description, together with a figure from 

 the type specimen, of 



lo spirostoma. — Shell conical, broadly ovate, horn-colored, spinous ; 

 spines short, thick, seven to eight on each whorl ; whorls about nine ; 



aperture ovate, about half the length of 



Fig 40 



the shell ; columella and outer lip much 



and regularly twisted, and forming a well- 

 defined sinus at base. 



Length of shell, 1| inches; breadth of 

 shell, li in. Length of aperture, 15-16 of 

 an inch ; breadth of aperture, h inch. 

 Habitat. — Tennessee. 

 Observations. — This is truly a most re- 

 markable species of this highly interesting 

 genus of mollusks ; its difl'orence from the 

 ordinary type of lo spinosa is too marked 

 to admit of its being confounded with 

 that, or indeed with any other species; 

 its stout, ovate form, short, heavy spines, and, above all, the peculiar 

 and graceful curvature of its outer lip, are prominent characteristics 

 and readily distinguish it. 

 Among several thousand specimens of Jo in my possession, but 



