46 



whorls in the European species, and the more abrupt termination 

 of the spire. 



Inhabits the Delaware river and many other waters of the United 

 States, in considerable numbers, and may be found plentifully, 

 during the recess of the tide, about the small streams through which 

 the marshy grounds are drained, in company with several other 

 shells. When kept in a vessel of water, like others of its kind, it 

 will proceed not only up the sides of its prison, but also along the 

 surface of the water, the shell downward, with regularity of motion 

 and apparent ease. In this case the reverted base of the animal is 

 concave ; and as the surface of the water is compelled to a corres- 

 ponding concavity, the pressure of the atmospheric column will ac- 

 count for the sustentatiou of the animal (whose specific gravity is 

 much greater than that of the water) in this singular position. It 

 occasionally crawls to the margin of the water to inhale a supply of 

 air; with this object the foramen is protruded to the surface, and 

 opened with an audible snapping sound, similar to that produced 

 by the resilience of the nib of a pen. 



There is a species of this genus that we have named Lymn^a 

 JUGULARis ; and which, in consequence of its having been found 

 but once, must be considered as a doubtful inhabitant of the United 

 States. It may be thus described. Shell tapering ; whorls about 

 six ; suture not deeply impressed ; aperture hardly equal to half 

 the length of the shell, but little dilated ; within brownish, particu- 

 larly upon the column, which is contracted in the middle ; outer 

 lip white, and almost imperceptibly repand within ; umbilicus very 

 distinct. Length one inch. 



A specimen was also brought from the West Indies by Mr. 

 L'Hermenier of Charleston. 



LYMNiEA HETEUOSTROPHA. — Shell sinistral, subovated ; color, 

 pale yellow, chestnut or blackish ; whorls four, the first large, the 

 others very small, terminating rather abruptly in an acute apex 3 

 aperture large, somewhat oval, three-fourths of the length of the 

 shell, or rather more ; within of a pearly lustre, often blackish : 

 lip a little thickened on the inside, and tinged with dull red. 



Inhabits with the first species, and almost as numerous. Plate 

 l,fig.6. 



Animal resembles that of L. catascoplum, but is of a darker 

 color and longer than its shell, the tentacula also are longer, and 

 setaceous ; tail acute. 



