MALACOZOA. GASTEROPODA. PECTIN1BRANCHIATA. 147 



and in their habits resemble the Littorinae. Most of 

 them may be found on the sandy beaches, along the line 

 of the last tide, or among shell sand. 



Rissoa is closely allied to Littorina, Melania, Phasianel- 

 la, Eulima, Odostomia, and several other genera. The 

 genus, as M. Deshayes remarks, was first " instituted by 

 M. de Freminville for some small shells observed by M. 

 Risso, a distinguished naturalist of Nice, and described 

 in 1814 by M. Desmarest in the New Bulletin of the 

 Philomathic Society." Dr. Fleming, in 1828, proposed 

 the genus Cingula for the same shells, in his History of 

 British Animals. In the second edition of Lamarck, M. 

 Deshayes defines the genus and describes forty-four 

 species. But in these works there are placed in the 

 genus some species which do not belong to it, while 

 some of its proper species are referred to other genera. 

 Those admitted here will, I think, be found to agree 

 with the above generic character. 



1. Rissoa ulucE. Salt-Marsh Rissoa. 



Shell oblongo-turrite, rather thick, opaque, somewhat cor- 

 neous ; the spire elongated, tapering to a small but bluntish 

 point ; the whorls seven, flattened, transversely obscurely ru- 

 goso-striate ; the last turn always more or less angulate ; the 

 suture distinct; the aperture ovate, acute behind, the peristome 

 thin, slightly reflected on the columellar side, leaving a narrowed 

 space between it and the whorl, and but partially concealing 

 the umbilicus; the exterior brown, olivaceous, or yellowish, 

 often crusted or corroded, the interior whitish. Length four- 

 twelfths of an inch, breadth a twelfth and a-half. 



Animal with the head, tentacula, and collar black ; the 

 mouth proboscidiform ; the tentacula tapering, with the eyes 

 near their base externally ; the foot subelliptical, yellowish- 



In great profusion, along with Littorina tenebrosa, in a 

 small salt-marsh, near Newburgh, on the Estuary of the Ythan, 

 where I first met with it in July, 1841. 



Turbo ulvae. Mont. Test. Brit. 318.— Cingula ulva?. Flein. Brit. 

 Anim. 308. — Littorina ulva?. Johnst. Beiw. Trans, iii. 270. 



