124 THE NAUTILUS. 



In a later paper, ( " On Geographic and Hypsometric Distribu- 

 tion of North American Viviparidae," Am. Jour. Sci., xlviii, 

 1894, pp. 132-141), however, he seems to have adopted Bin- 

 ney's conception of coarctata, which he recognizes as a valid 

 species. In connection with C. subsolidum, he states that "to 

 the south of Missouri, it is replaced by its congener, Campeloma 

 coarctatum Lea". And on p. 137, he says "over all the 

 states from Arkansas south to Texas and east to central Ala- 

 bama ranges a form, to which Mr. Lea gave the name of Camp- 

 eloma coarctatum. It appears to be most nearly related to Camp- 

 eloma subsolidum, being related to it as Campeloma lima, is related 

 to Campeloma rufum ' ' . 



From a careful study of a very considerable amount of ma- 

 terial from Alabama, Mississippi, Louisiana, Texas, Arkansas 

 and Missouri collected by Wheeler, H. H. Smith, Hinkley, 

 Singley and others, including the Lewis collection, I have come 

 to the conclusion that Dr. Lewis was entirely right in his judg- 

 ment as to these several forms. Figures 4 to 7 on my plate 

 are from shells in his collection and no doubt, were considered 

 by him at the time he prepared his Alabama Catalogue. 



Lea's incrassata is a deformed, depauperate specimen. Mr. 

 W. B. Marshall of the National Museum has kindly compared 

 the original of my figure 4 with Lea's type and writes : " It is 

 like Lea's type of incrassata in practically every detail. Your 

 shell is a trifle larger". Figure 5 is a larger example of the 

 same kind, less aberrant and connecting up directly with the 

 typical form. Figure 6 is the typical coarctata of Lea and is 

 also the normal 3 7 oung shell of Try on' s nolani. Figure 7 is the 

 mature form of fig. 6 and the usual manifestation of the Coosa 

 form known as nolani. It grows larger than that occasionally 

 and is frequently more inflated. But, on the whole, the Ala- 

 bama form is differentiated from the typical ponderosum of the 

 Mississippi system by its more elongated, more cylindrical and 

 less inflated form. I have seen no specimens that agreed ex- 

 actly with Tryon's figure 10. It would seem either to be an 

 extreme, aberrant example or to have had its peculiarities ex- 

 aggerated in drawing. But there can be no doubt but that the 

 three forms described as incrassata Lea, coarctata Lea and nolani 



