MARINE MOLLUSCA OF THE UNITED STATES. 83 



3. R. robusta, H. C. Lea. Fig. 155. 



(Cingula.) Bost. Proc. 288, t. 24, f. 4. 1844. 



Shell ovate-acuminate, perforated, smooth, thick, white; spire 

 short, subacute ; suture impressed ; whorls five, somewhat angled 

 at the superior suture; last whorl round ; base smooth; perfora- 

 tion narrow, profound ; mouth ovate, large. 



Length 2.5, diam. 2 mill. 



Cape Map, i\T. J. 



This is a somewhat doubtful species : it (as well as the next) is 

 perhaps only the young of a form of B. latior. Only one speci- 

 men was obtained. 



4. R. modesta, H. C. Lea. Fig. 15G. 



(Cingula.) Bost. Proc. 288, t. 24, f. 5. 1844. 



Shell ovate, imperforate, smooth, thin, diaphanous, greenish 

 horn-color; spire short, ovate, not acute; suture small; whorls 

 four, flattish; last whorl round ; base smooth ; mouth ovate ; acute 

 above, rounded below. 



Length 2.5, diam. 1.8 mill. 



Quite common on the under surface of stones below high-water 



mark. 



Long Island (near Brooklyn). 



5. R. turricula, H. C. Lea. Fig. 157. 



(Cingula.) Proc. Bost. Soc. Nat. Hist. 289, t. 24, f. 6. 1844. 

 Shell elevated, conic, perforate, smooth, thick, tawny ; spire 

 very much exserted, conical, obtuse, sutures small ; whorls six, 

 convex ; last whorl slightly bullate ; base smooth ; perforation 

 small, narrow, lunate; mouth ovate; columella thick, almost dis- 

 joined from the last whorl. 



Length 3, diam. 1.3 mill. 



South Carolina. 



This species has not been detected or identified by subsequent 

 collectors. 



6. R. aculeus, Gould. Fig. 158. 



(Cingula.) Invert. Mass. Edit. 1, 266, f. 172. 1841. 



Shell minute, subcylindrical, elongated, fragile; whorls six, very 

 convex, with a deep suture; with numerous revolving lines and 

 traces of longitudinal folds towards the apex. Aperture small, 

 suboval, oblique. Light horn-color. 



Lenoth 5 mill. 



