[42 ] 

 GASTRODONTIN^. 



Geneva. 

 ^ Not dentate. 



1. Mesomphix, Eafinesqne. 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 to the basal axis of the shell. 



** Lamellarhj denPite. 

 f Outer whorl dentate. 



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



laminie revolving Avithin the base. Surface nearly 

 smooth, polished. 



ff Outer icliorl and columella both dentate. * 



4. Stkobila, Morse. Shell minute, with lamiucne both on 



the base and the colunieUa. Surface strongly striate. 



MESOMPHIX, Raf. 



a. Diam. = 10 — 15 mill. 



1. Mesomphix intertexta, Binney. 



Plate 4, figure 33. 



Subglobose, whorls 6 — 7, closel}^ 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. Yery convex below. 

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

 a calcareous deposit within ; umbilicus small. 



Diam. 19 mill '^l' ■> (^M ."7r.c:-irY" ^c." 



Western New York to Georgia, and westward to Missouri 

 and Iowa. 



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

 an^'-led periphery and bands of color, when present, oft'er dis- 

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

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



