17 



with the existence of a carinated line only in its young statr 

 having increased to four volutions, the carina is no longer 

 formed. 



M. undulata. Shell large, elevated, conic, brownish, with a 

 bro id, equally impressed hand 5 inferior boundary of the band 

 elevated and deeply crenatc; superior boundary elevated 

 sometimes nodulous: volutions at least eight, not convex: suture 

 not impressed, hardly obvious, undulated by revolving on the 

 inferior crenate boundary of the impressed band: labrum,nea.i 

 the base, much protruded: sinus very obtuse. 



Length, one inch and four-tenths. Inhabits the Ohio. 



I observed this large species to be abundant in Kentucky 

 River, when traveling in that State two years since with Mr. 

 Maclure. 



It seems to approach nearest in character to the canali ulata, 

 Nob., but its rough appearance will distinguish it c\cu at lirst 

 sight. 



M. stygian Shi 11 robust,ovate conic, black: spire rather Ion:: 1 

 than the aperture, eroded at tip: volutions five, hardly convex: 

 wrinkles obsolete, excepting a few larger ones: suture not pro- 

 foundly indented: aperture narrowed at base into a slight sinus 

 and subangulated; much widest in the middle: labium much 

 arquated in the middle. 



Length, three-fourths; greatest breadth, less than half an 

 inch. 



A specimen of this shell was given to me L< sueur; 



several were found in Cumberland River, by Dr. Troost. In 



form it resembles armifera, .\ob., more than any other spe< 

 but that shell is armed with tubercles and ornamented i>\ co 

 lored lines, its suture also is only a simple impr< 



M. laqueaia. Shell oblong: spire longer tha 1 the aperture. 

 elevated, conic, acute: volutions moderately convex, with abou 

 seventeen regular, elevated, equal, equidistant costae on the 

 Buperior half of each volution extending from suture to suture^ 

 and but little lower, and becoming obsolete on the I"..!-, whirl; 

 suture moderately impressed: sinus obsolete. 



Length, four-fifths of an inch. 



This species was found by Dr. Troost in Cumberland River. 

 Aside from a difference in form, it may b • distinguished from 

 ■ Hutu* Nob., and catenaria^ Nob., bj h< ing altoj 



• > 



