EASTERN PROVINCE INTERIOR REGION SPECIES. 



31i 



Fig. 33G. 



60-1-GO teetb, witb 11 laterals. This species is peculiar in having 

 extremel}' long cutting points to the single cnsp of its marginal -teeth ; 

 the very extreme marginals have this cutting point bifid, and also 

 have a small side cutting point. A similar dentition is found in 

 dausns and ^yh€atley^. (See also Fig. 7, on p. 49.) 



The genital system is figured by Leidj' {I. c). The penis sac is 

 short, stout, cylindrical, receiving the vas deferens and retractor mus- 

 cle at its summit; the genital bladder is small, elongated, bluntly 

 tapering at its apex, on a short, narrow duct; the oviduct is greatly 

 convoluted. 



In the Southern and Southwestern States, from ITorth Carolina to 

 Texas, the species assumes often, not in all localities, the 

 form described as huccu'lentns. I repeat the description and 

 figures of the ty])ical form and a small variety from Ala- 

 bama (Figs. 33G, 337). This last often wants the parietal 

 tooth ; this form has same jaw, lingual membrane, and geni- 

 talia as typical ihyroides. 



Shell usually perforate, globose-conic, more or less ele- 

 vated, rather thin, shining, pale yellowish-green, surface regularly and 

 delicately furrowed by the strife of growth ; whorls 5 or a little more, 

 rounded, and separated by a well-impressed suture; base convex; 

 aperture rounded ; peristome forming nearly two-thirds of a circle, 

 rather broadly reflected, white, somewhat tiesh-colored behind, not 



Fig. 337. 





M. bvcculentus. 



completely covering a small umbilical i)erforation5 sometimes entirely 

 covering it ; parietal wall sometimes bears a small white tooth at the 

 middle, but oftener uot. Greater diameter 38^, lesser 15^™"; height, 

 lO^"'". (Terr. Moll., Ill, Plate XF, a.) 



Mesodon clatssus, Say. . 

 Shell subim perforate, conoidly semi globose, rather solid, with 

 crowded, rib-like strife, yellowish horn-color ; spire sub- ^^^ ^^g 

 regularly conoid ; whorls 5i, rather convex, gradually in- 

 creasing, the penultimate subangular, the last rounded, 

 anteriorly subcoustricted, and briefly deflected ; umbilicus 

 narroWj almost covered by the reflected peristome) aper- 



M, elausus. 



