[42 ] 

 GASTEODONTINiE. 



Gene'a. 

 * Not dentate. 



1. Mesomphix, Eafinesque. Shell moderate in size, um- 



bilicate or perforate ; aperture obliquely semilunar. 



2. CoNULUs, Fitzinger. Shell minutely conical, imperfo- 



rate or perforate ; aperture depressed transverse, its 

 lower margin extending te the basal axis of the shell. 



** Lamellarly dent'ite. 

 f Outer whorl dentate. 



3. Gastrodonta, Albers. Shell minute, with one or more 



laminae revolving within the base. Surface nearly 

 smooth, polished. 



ff Outer whorl and columella both dentate. 



4. Steobila, Morse. Shell minute, with laminse both on 



the base and the columella. Surface strongly striate. 



MESOMPHIX, Eaf. 



a. Diam. = 10^-15 mill. 



1. Mesomphix intertexta, Binney. 



Plate 4, figure 33. 



Subglobose, whorls 6 — 7, closely striated, sometimes with 

 very faint revolving lines, yellowish horn color, slightly 

 angled, and sometimes with a light and beneath it an ill-de- 

 fined brown band at the periphery. Very convex below. 

 Aperture ob'ique, narrow lunate, base of shell thickened by 

 a calcareous deposit, within ; umbilicus small. 



Diam. 19 mill. 



Western New York to Georgia, and westward to Missouri 

 and Iowa. 



Larger than the next, and not quite so conical; the slightly 

 angled periphery and bands of color, when present, ofier dis- 

 tinctive characters. . The shell is also thicker and not so pel- 

 lucid, and frequently exhibits spiral lines, not visible on ligera. 



