210 
In the following descriptions the shells are considered sinistra!. 
Planorbis lentus. — Desc. Shell dull brownish or yellowish 
brown, sub-carinate above, particularly in the young shell ; whirls 
nearly five, striate across with five, raised, sub equidistant lines, 
forming grooves between them ; spire concave ; aperture large, em- 
bracing a large portion of the penultimate volution j labrum more 
acutely, but not very prominently arquated above, its basal portion 
horizontally subrectilinear in the adult and not extending below 
the level of the base. 
Ohs. I obtained this species in the canal at New Orleans and I 
indebted to Mr. Maclure and also to Mr. Barabino for many fine 
specimens collected in the vicinity of that city. I also found the 
same species at Ojo de Agua, Mexico, when travelling in that 
country with Mr. Maclure. It differs from the following species 
in having the labrum less prominent above, and the basal portion 
of this part being in the adult horizontally subrectilinear so as not 
to touch a plane on which the base of the shell may rest ) the 
aperture also is more transverse. PL 54, fig. 1. 
Planorbis trivolvis. — -P. trivolvisy N., Amer. Ed. of 
N'icholson’s Encyc.^ Article Conchology ^ pi. 2, f. 2. 
GocJilea, trium orhiuniy Lister^ Conch, pi. 140, f. 46. 
Petiver, Gazophyl. pi. 106, f. 17. 
Ohs. This is an inhabitant of the Middle and Northern States 
and is very common in many districts. I have found it in Penn- 
sylvania, New Jersey, Delaware, Maryland, Falls of Niagara, 
Upper Canada, and in the vicinity of Council Bluff on the Missouri. 
Dr. Eights sent me specimens from Albany, New York, and 
Mr. Jessup gave several from Cayuga lake. Lister gives two 
pretty good figures of this shell and quotes Virginia as the native 
locality. Muller, Glmelin and Dillwyn, incorrectly referred to 
Lister’s figures as Helix alhella, but the latter author in his edition 
of Lister agrees with us in considering them as representations of 
the present species. PI. 54, fig. 2. 
Planorbis bicarinatus, S. Amer. Ed. of Nicholson^ Encyc. 
Article Gonchology, pi. 4. 
Helix angulatus, Racket. Linn. Trans, -yo?. 13, 42, 5, 
.fig- 1 - 
P. hicarinatus^ Sowerhy’s Genera. 
Ohs. It is an inhabitant of the same extensive region as the 
