LIMNAID. 101 
individual is able, at the same time, to perform the function of 
each sex with two others. 
Bulimnexa megasoma, Say (ciii, 5), is partially carnivorous 
(Wetherby . Mr. Whitfield has recorded some singular changes 
produced in successive generations, the progeny of a single indi- 
vidual, confined in an aquarium. They gradually diminished in 
size and the male organs disappeared. Prof. Hyatt has ascribed 
these changes to different conditions of temperature, but it was 
probably due also to deficient food-supply, and an effect of the 
physiological law to which Mr. Meehan has so frequently called 
attention in plants, namely, of the greater persistence, in cases 
of depauperization, of female functions and members. 
LYMNUS, Monti. Typical. (Auricula, Klein.) JZ. stagnalis, Linn. 
(cili, 9). 
RADIX, Montf., 1810. (Neristoma, Klein [teste Adams]. 
Gulnaria, Leach [teste Turton ].) Shell suboval-globular; last 
whorl ventricose; aperture very large; columella plaited. ZL. 
auricularia, Linn. (ciii, 6). 
POLYRHYTIS, Meek. Much like the last in form, but bearing 
distinct, regular, vertical costae. L. Kingi, Meek. ‘Tertiary ; 
Utah. 
BULIMN#%A, Haldeman, 1841. Shell oval, subglobular, large, 
the spire short, apex sharp; aperture moderate. JL. megasoma, 
Say (clii, 5). 
LIMNOPHYSA, Fitzinger, 1833. Shell oval-oblong, spire elevated ; 
aperture narrowly ovate, about half the length of the shell. JZ. 
reflexa, Say (ciii, 7). 
LEPTOLIMN#A, Swainson. (Omphiscola, Raf.) Shell nearly 
cylindrical; spire thick, lengthened; aperturesmall. JL. glabra, 
Mull. 
ACELLA Hald., 1841. Shell elongated, very slender; whorls 
4-6, very oblique, but slightly convex; aperture small, ovate, 
expanded below. L. gracilis, Jay (ciii, 8). 
PLEUROLIMNZA, Meek. Shell differing from the last in having 
small, regular surface-coste parallel to the lines of growth, 
and aperture narrowed or subangular, instead of rounded ante- 
riorly. L. tenuicostata, Meek and Hayden. Fossil. Eocene; 
Dakotah. ?— Acella. 
VELUTINOPSIS, Sandberger. Oval, neritiform, spire excavated, 
last whorl very large, columellar lip depressed. LZ. velutina. 
Desh. ‘Tertiary; Crimea. 
Some of the species of Limneza inhabiting the Sandwich 
Islands and New Zealand are sinistral. Limnza adapts itself to 
very diverse conditions; it is found in Greenland and Iceland, 
in hot and sulphurous springs, in fresh or brackish water. JL. 
Hookeri occurs in Thibet, at an elevation of nearly 14,000 feet ; 
LL. abyssicola in the Lake of Geneva, at a depth of 800 feet. 
