318 Monograph of the Gasteropoda. 



Plenrotoniaria Hall!. — (S. A. Miller). 



Fig. 34 — Pleurolomaria ffalli, maguilied two diameters — apex broken off. 



Shell rather small, about two whorls, rapidly enlarging toward the 

 aperture ; spire short ; slightly convex on top and plain below, with 

 the exception of the projecting aperture, and marginal band, giving it 

 in one view a plano-convex appearance ; umbilicus closed ; edge of the 

 outer volution marked with a sub-cylindrical band, leaving a slight 

 depression on the upper and a marked curved groove on the lower side ; 

 aperture rapidly expanded below and notched at the band. 



The specimen figured has the shell partly removed from the last 

 whorl, and the upper side so worn as not to show any surface mark- 

 ings. The band at one place shows rovolving lines. The lower side 

 seems to be well preserved, and has no surface markings. 



I found this specimen about 340 feet above low-water mark, and do 

 not know of another specimen at this time. 



The specific name is given in honor of J. W. Hall, Principal of the 

 Covington schools, curator of paheontology in the Cincinnati Society of 

 Natural History, and famous, too, for his peculiar trait of collecting 

 large quantities of fossil corals, and making the rough places smooth. 



Genus Raphistoma — (Hall, 1847). 



[Etym. — Gr. raphe, a seam or suture, and stoma, mouth ; from the 

 suture or seam-like appearance in the upper side of the aperture.] 



Shell depressed, turbinate ; discoidal spire, with three to five volu- 

 tions ; suture close ; umbilicus moderately large ; aperture subtrigonal; 

 upper side of the volutions marked by a kind of seam or suture, pro- 

 duced by the sudden tendency backward of the striae, which leaves a 

 slight notch in the edge of the aperture. 



The slight notch in the upper edge of the aperture, which is marked 

 in the progressive growth of the shell, by a simple seam or bending in 

 the striae, is somewhat similar to the notch and band of Pleurotomaria; 

 but the outer angle of the volution presents no band, but a simple 

 bending of the stria?. 



