OF CONCHOLOGY. 43 



JJ Shell suhangulate on the periphery. 

 8. Mesodon Roemeri, Pfeiffer. 



Plate 8, figure 4. 



Shell depressed, rather thin, semi-transparent, closely, but 

 faintly striate ; spire a little elevated, suture slightly im- 

 pressed ; whorls 5, somewhat convex, the last one subcarinate 

 or angulate on the periphery, scarcely descending to the 

 aperture; aperture obliquely lunate, the lip well thickened, 

 but hardly expanded above, though becoming towards the 

 base well-reflected, covering partially the umbilicus, and rarely 

 entirely closing it ; parietal wall generally armed with a well- 

 developed tooth. Horn-colored. 



Diam. 21, height 10 mill. 



Texas. 



May be distinguished at once from all the other species by 

 its depressed form and angulate periphery. 



** Not dentate. 



f Umhilicus closed. 



X Unicolored. 



9. Mesodon major, Binney. 



Plate 8, figure 5. 



Yentricose, convex, globosely turbinate, heavy, covered with 

 coarse oblique strise ; spire, elevated, convex, suture well im- 

 pressed; whorls 6, convex, the body whorl very large and 

 subglobular, very slightly declining ; aperture small, rounded 

 lunate, lip thick, moderately wide, with a tooth-like elevation 

 at the base near the body whorl, dilated and covering the um- 

 bilicus. Yellowish brown. 



Diam. 4-4, height 33 mill. 



Tennessee to Florida and Alabama. 



Dr. Binney first described this as a species distinct from M. 

 alholabris, and separated it on account of its larger size, more 

 globose, elevated form, rounder aperture, coarser striae, &c. 

 Messrs. W. G. Binney, Newcomb, Gould and myself admit its 

 validity, but Mr. Bland, on the contrary, unites the two, 



