RISSOA. 301 



Rissoa Mighelsi. 



Cingiila nrenan'a, Mighels and Adams, Bost. Journ. iv. 49, pi. 4, fig. 24 (1842), not 



Tiirho arrmvius, JNIoxTAGU. 

 Rissoa M'Kjhelsi, Stimpsox, 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 

 inch ; divergence, thirty degrees. 



Casco Bay, taken from the stomach of a haddock in the ^-^1,^^''" 

 summer of 1841. 



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

 J. W. Mighels {Mig-hels and Adams'). 



Rissoa exarata. 



Rissoa exarata, Stimpson, Proc. Bost. Soc. iv. 15 (1851) ; Shells of New 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 

 dredo-ed in three fathoms, on a shelly bottom in Boston ta. 



. , , . . , . Enlarged. 



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 below, plicated above ; 

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



Cingula carinata, Mighels and Adams, 1. c in remarks. 



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



not Turbo semicostatiis, Moxtagu. 

 Rissoa pelagica, Stimpsox, Bost. Proc. iv. 15 ; Shells of New England, 34. 

 Rissoa carinata, Stimpsox, Check Lists, 4. 



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

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



