340 TRANSACTIONS OF THE WAGNER FREE 



Rissoa athymorhyssa n. s. 

 Plate 20, figure 13 b. 



Pliocene of Shell Creek, Florida, Willcox. 



Shell small, oblong, with a little more than four and a half rounded 

 whorls, slightly angulated at the shoulder and constricted just in front of the 

 appressed suture ; surface without perceptible spiral sculpture, apical whorls 

 smooth, the last two whorls marked by regular low, somewhat flattened, trans- 

 verse wrinkles, with narrower interspaces, which become obsolete on the base ; 

 aperture ovate, edge simple, continued over the body by a thin callus; pillar 

 thin, arched; base imperforate. Alt. 2.5 ; max. diam. 1.2 mm. 



Only a single specimen was obtained. 



Subgenus Onoba Adams. 



Rissoa (Onoba) geraea n. s. 



Plate 21, figure 13 a. 



Newer Miocene of the Cape Fear River, N. C, at Mrs. Purdy's marl-bed, 

 Johnson. 



Shell thin, subovate, with a subacute apex and five or six gently-rounded 

 whorls ; suture distinct, but not deep ; apical whorl very minute, smooth ; sub- 

 sequent whorls evenly spirally striated, with the interspaces slightly wider 

 than the striae, the latter a little more distant and slightly'coarser on the base, 

 especially near the umbilical region; the striae increase by intercalation, and 

 hence appear alternate here and there ; base produced ; aperture ovate, angu- 

 lar behind, the inner lip a little concavely flexuous, reflected against the body, 

 producing a more or less conspicuous chink, but with no perforation behind 

 it; margin in the fully adult obtuse and internally thickened, continuous over 

 the body ; in the young the anterior end of the reflected pillar-lip projects 

 slightly; in the adult this projection is hidden by the lip-deposit. Alt. 4.5; 

 max. diam. 2.5 mm. 



Rissoa (Onoba) gersea var. minor Dall. 



Shell slightly smaller, and with slightly finer sculpture ; the umbilical 

 chink less wide or even .obsolete. Alt. 3.5 ; diam. 1.75 mm. 



Pliocene of the Caloosahatchie beds, Dall. 



These shells are so much alike, in spite of the difference in size, that I 

 hesitate to separate them even varietally, but it is probably best to keep the 

 differences in mind, since, from the material I have been able to examine, they 

 would appear to be characteristic of the older and newer horizons. It may 

 be, however, that more material will show them to intergrade. The specimen 

 figured is from the Miocene. 



