A GENUS DOLIUM. 
to be connected with my second group; and which, uniting all 
the characters observed in the Tuns, ought naturally to take its 
place among them, under the name of Doxium latilabre. In 
the same work this author gives, under the name, of Mara 
crasstlabris, a shell which I consider as a variety of the first ; 
the only differences which this author himself has found, consist 
in the smallness of the shell, in the spire, which is a little more 
prominent, and in the thickness of the right lip, characters 
which appear to me too little specific, and too variable to deter- 
mine its separation as a species. We shall find also in. this 
series the Doxtum pomum, which approaches exceedingly to 
the Dottum latilabre in the form of its aperture, in the ridges 
which exist upon the columella, and particularly in the right lip 
which is widened, and has, internally, folds, or very strongly 
prominent denticulations. 
The animals of the Tuns are in general strongly colored, and 
painted with different tints which form bands and spottings upon 
their entire exterior. These animals are often found in rapid 
waters, and upon pebbly bottoms; their motions are quick. The 
species seen upon our coasts appear towards spring, and in 
summer: the other species inhabit warm climates. 
A. Species with the right lip always thin and undulated. 
1. DOLIUM PERDIX, Lam. The Partridge Tun. 
(Collect. Mass. Lam.) Lasr., Conch., t. 984, fig. 43. 
Pl. V, fig. 9. 
D. testa ovato-oblonga, inflata, tenui, fulvo-rufescente, maculis albis 
lunatisque seriatim notata ; costis convexiusculis, confertis ; spird exserti- 
uscula, conica. 
Shell ovate-oblong, ventricose, pretty thin, of a reddish 
brown color, pleasingly varied with white spots in transverse 
series, for the most part semi-lunar, and more or less distant ; 
spire slightly projecting, conical, pointed, composed of from 
five to six whirls which are furnished with numerous ribs, 
