18 LAND AND FRESH-WATER SHELLS OF N. A. [pART IV. 



resembles the J\I. armigera (Say), in most of its characters, but may 

 at once be distinguished by the double row of tubercles, the 

 armigera never possessing distinctly more than one row ; below the 

 sutures, however, there are sometimes imperfect tubercles, which 

 are caused b}' the pi-otrusion of the tubercles of the superior whorl. 

 This protrusion also takes place in the Jayana, but causes in it only 

 a constant curvature in the linear suture. 



The apex of the specimen is much eroded, and consequently I am 

 not sure of the number of the whorls, probably eight or nine. The 

 aperture may be rather more than one-third the length of the shell, 

 and is acutely angular at the base, with rather a deep sinus. The 

 callus above causes a considerable sinus there. 



The operculum is dark brown, the radii converging at the lower 

 interior edge. — Lea. 



This shell nnd Mr. Anthony's M. robulina are entirel}^ iden- 

 tical in every respect, the species being a A-ery constant one in 

 all its characters, as I am unable to select from a considerable 

 number of specimens any which exhibit variations from the. 

 t^'pe form. It is an exceedingly abundant species, and very 

 remarkable for its peculiar armature and the narrowed canal, 

 suggestive of the genus lo. 



The following is the description of 



Melania rohnlina. — Shell solid, ovately rhomboidal, corneous, 

 encircled with brown bands ; whorls six, bearing a double series of 

 nodules, the upper one immersed in the suture ; aperture rhomboidal 

 produced into a rostrum, callous behind. 



JlabUat. — Cumberland River, Tennessee. 



Long. 1 ; lat. 5-8 poll. 



Observations. — Of the same size as M. armigera, Say, but differs in 

 coloration; the rostrum is much longer, and the posterior series of 

 tubercles much more developed. — Anthony. 



