EASTERN PROVINCE SOUTHERN REGION SPECIES. 389 



MESODOIV. (St>e p. 294.) 

 Mesodota Rocsncci, rriciFi-'Eii. 



Shell with a narrow or i)artially covered umbilicus, sometimes im- 

 perforate, depressed, rather thin, closely- striated, rather . ^^^ ^23. 

 transparent and smooth, horn-colored; spire slightly 

 elevated; suture lightly impressed; whorls 5, rather 

 convex, increasing slowly, the last one subcarinate at 

 its periphery, scarcely descending; aperture lunar, ob- 

 lique, generally slightly contracted by a parietal denti- 

 cle which obliquely enters the mouth of the shell ; per- 

 istome white, thickened, the ujjper portion hardly ex- 

 panded, reflected below, and at the columellar junction spreading into a 

 thin, partial covering to the umbilicus. Greater diameter 21, lesser 

 18""" ; height, 10"°^. 



HcUx Hoenieri, PfkifferJii Roemer's Texas, 455 (1849); Zeitschr. f. Mai., 1848, 117.— 



Reeve, Cou. Icon., No. 6S0.— W. G. Binxey, Terr. Moll., iv, 55 ; L. & Fr.-W. 



Sli., i, 146, lig. 250 (1869). 

 Hdix deniifira, part, Pfeiffer, Mod. Hel. Viv., iii, 269; io Chemnitz, ed. 2, 331, pi. 



cxxxi, fi^s. 1-3, not of Binney. 

 Mesodon Ixoeineri, Thyon, Am. Jouru. Conch., iii, 43 (1867). — W. G. Binney, Terr. 



Moll.. V, 3:29. 



Near New Braunfels, Tex.; Washington County, Williamson County, 

 Bosque County, and Colorado Eiver, Texas. A species of the Texas 

 Subregion. 



This species was formerly confounded b^' Pfeiffer with denfifera, an. 

 authentic specimen of which he had not seen. It is quite a distinct 

 species, and inhabits a distinct geographical region. It may be distin- 

 guished from dentifera most readily by attention to the following jnir- 

 ticulars: Its umbilicus is generally but partially covered, while dentifera 

 is always imperforate; its color is lighter, its surface smoother, and, 

 above all, its peristome is not so broadly reflected; it is also distinctly 

 subcarinate at the periphery. 



Jaw as usual ; 7 ribs on one, 9 on another specimen examined. 



The lingual membrane (Terr. Moll., Y, Plate YlII, Fig. C) has 35-1- 

 35 teeth, with 12 laterals. A few of the last laterals may have side 

 cusps and cutting points. 



The genitalia are figured on Terr. Moll., V, Plate XT, Fig. J. The 

 oviduct is scarcely convoluted. The genital bladder is large, oval, with 

 a long, large duct. The penis sac is short, stout, of about equal breadih 



