VALLONIA. 247 



Section ORTHOSTYLUS Fer. 



Vol. VIII, p. 34. C. cossmanniana is merely a form of^C. 

 quadrasi, the inter gradation being proven by a series of specimens 

 sent me by v. Mollendorff, who holds the same opinion. 



Genus VALLONIA Kisso. (Vol. Ill, p. 169.) 



NOTE. The following account of this gen us has been contributed 

 by DR. V. STERKI of New Philadelphia, Ohio. A more detailed 

 monograph will be found in the Proc. Acad. Sci. Phila. 1893. 



Shell minute (l'8-3*5 greater diam.), openly umbilicated, with 

 flat or moderately elevated spire, colorless or yellowish to reddish 

 horn colored, transparent or diaphanous, without bands or markings 

 of any kind, surface finely striated or with membranous ribs; 

 whorls 3-4, rounded ; aperture nearly circular or transversely some- 

 what elongate; peristome everted or straight, with or without a 

 whitish lip. 



The last whorl, in the majority of the species, descends in front to 

 the aperture, either as a whole or at the suture only, while the back 

 of the whorl keeps straight to the very margin. Also in a number 

 of species the last whorl ascends distinctly before it descends (see 

 pi. 33, figs. 33, 37). These features, not pointed out in previous 

 descriptions, are quite marked and characteristic in certain forms. 

 In size it must be said that the altitude of the whole shell is given. 



The soft parts are like those of Helix externally, whitish translu- 

 cent ; a few pale yellowish spots in the mantle, near its edge, is all the 

 pigment seen. The pedal disc is comparatively small, about as long 

 as the diameter of the shell ; eye peduncles slender, tentacles short 

 but distinct. Jaw rather stout, rather short, arcuate, ends attenu- 

 ated, rounded or truncate, with irregular sharp rib-like stride, dentic- 

 ulating the cutting edge, which, in some forms, shows a slight, wide, 

 median projection. On the back of the jaw, about the middle, 

 there is a strong transverse lamella which passes into the tenaculum 

 membrane. Radula with 65-85 transverse rows of 23-35 teeth ; the 

 median narrow, its reflection having three very small cusps ; laterals 

 5-6, or fewer, with a rather strong mesodont and a short ectodont 

 becoming two-pointed in the outer ones. Marginals wide, short, 

 pectinate rather than serrate, as their 5-7 cusps are long and slender 

 like the teeth of a comb ; the one or two outer teeth have hardly any 

 perceptible cusps. 



