EISSOA. 301 



Rissoa Mighelsi. 



Cingnla arenaria, Migiiels and Adams, Bost. Journ. iv. 49, pi. 4, fig. 24 (1842), not 



Turbo arenarius, Montagu. 

 Rissoa Miijhehi, Stimpson, Proc. Bost. Soc. iv. 15 ; Check Lists, 4. 



Shell minute, white, sub-cylindrical, sub-plicate longitudinally, 

 and minutely striate transversely ; spire elongated, conical ; 

 whorls six, convex ; suture impressed ; aperture sub-orbicu- 

 lar, half the length of the spire ; operculum horny. Length, 

 ten hundredths of an inch ; breadth, five hundredths of an 

 mch ; divergence, thirty degrees. 



Casco Bay, taken from the stomach of a haddock in the ^.f^^''- 

 summer of 1841. 



But few specimens have been found, which are in the cabinet of 

 J. W. Mighels {Mig-hels and Adams}. 



Fig. 570. 



R. e.rn ra- 

 ta. 

 Enlarged. 



Rissoa exarata. 



Rissoa exarata, Stimpson, Proc. Bost. Soc. iv. 15 (1851) ; Shells of Ncav England, 34, pi. 

 1, fig. 3 ; Check Lists, 4. 



Shell small, ovate, fuscous, rather solid, imperforate ; whorls 

 five, rather convex, sub-plicate posteriorly and bound by in- 

 equidistant, elevated, transverse ribs, three on upper whorls; 

 aperture small, ovate, peristome thickened. Length, eleven 

 hundredths of an inch ; breadth, five hundredths of an inch. 



A single specimen of this very distinct species was 

 dredged in three fathoms, on a shelly bottom in Boston 

 Harbor. It is distinguished by its very prominent, distant, 

 transverse ribs, which are three on the upper whorls and eight on 

 the lower. Its aperture is very small (^Stimpson}. 



Rissoa carinata. 



Shell very small, ovate ; whorls five, convex, carinated beloAV, plicated above ; 

 spire conical ; suture strongly impressed ; aperture sub-orbicular ; operculum horny. 



Cinr/ula carinata, Migiiels and Adams, 1. c, in remarks. 



Cimjula ssmicostata, Mighels and Adams, Bost. Journ. N. H. iv. 49, pi. 4, fig. 23 (1842), 



not Turbo ssmicosiattis, Montagu. 

 Rissoa pelajica, Stimpson, Bost. Proc. iv. 15 ; Shells of New England, 34. 

 Rissoa carinata, Stimpson, Check Lists, 4. 



Shell very small, ovate-conical, of a ferruginous red color, very 

 thin, whorls for the most part five, convex j with longitudinal ribs 



