OF CONCHOLOGY. 195 



An elegant species, closely allied to H. tenellus, Reeve, but it 

 has a longer last whorl and a narrower aperture. 



This shell is very interesting, as it indicates a decidedly fresh 

 water genus in this fossil group ; a genus living in South Ameri- 

 can rivers. 



DYRIS, Conrad. 



Subulate, with many volutions ; aperture ovate ; labium re- 

 flexed. 



The mouth of this shell is similar to that in the genus Melania, 

 but the form and sculpture of the shell are very different from 

 those of 3Ielania. 



D. GRACILIS, Conrad. — PI. 10, fig. 8. 



Very slender and elongated ; whorls 8, convex, revolving 

 lines carinated, very regular, 4 on the penultimate and 5 on the 

 last whorl ; about the sutures there is a rather wide indented 

 space, whorls minutely and obliquely striated. 



The figure is a rough outline, merely indicating the natural 

 size. 



NP]RITINA, Lam. 



N. Ortoni, Conrad.— pi. 10, fig. 5, 11. 



Thick, transversely suboval ; spire very small, of 3 whorls, 

 last whorl flattened on top ; aperture expanded ; margin of inner 

 lip very slightly concave, acute, densely and minutely plicated ; 

 labrum summit nearly on a line with the apex, which is entire, 

 colored markings generally zigzag brown longitudinal lines. 



N. pupa, Gabb (not Lin.), Amer. Journ. Conch, vol. 4, p. 197, 

 pi. 16. 



This species is widely different in form and size from N. pupa. 

 Mr. Gabb had only young shells to describe from, but in the 

 present collection are 15 specimens of various ages, figure 11 

 representing the actual size of a full grown shell. Fig. 5 repre- 

 sents a variation in the pattern of colored markings. 



N. pupa is probably about one-third the size, and has not the 

 flattened form of the area of the spire. 



BULIMUS, Scopoli. 

 B. LINTEUS, Conrad. — PI. 10, fig. 9. 



Acutely ovate, thin in substance, whorls 5, those of the spire 

 slightly convex, suture impressed ; last whorl slightly carinated 

 at the suture, elongated ; surface minutely reticulated with ru- 

 gose lines ; columella arched, not plicated ; peristome not pre- 

 served. 



