340 
On thè genus Pompholyx and its Allies, 
shape, containing four or fi ve otoconites. The tentaci es are re- 
tractile at thè bases, but only slightly so near thè extremities. 
The ava. These are laid on stones, shells, or thè leaves of 
plants. They are covered by a round, flattened, slightly tuber- 
culate capsule of leathery consistence, quite insoluble in water, 
alcohol, or glycerine. It is thin, brownish, and nearly transpa- 
rent. These capsules are disk-like, and cover froin five to ten 
ova, placed in a single layer embedded in a brownish jelly. 
Each ovnin is contained in a transparent, tongh, ovai envelope. 
Those which I bave exainined contain all stages, froin thè siin- 
ple ovum to thè embryo molhisk encased in a shell of a single 
whorl, and with thè eyes, tentacles, and viscera well advanced. 
The first indication of organization is thè separation of thè vis- 
eeral mass from thè embryonic foot. The mantle, eyes, and 
shell are developed early, but thè tentacles only miich later. 
The ova are deposit^d in thè inonths of May and dune. 
Notwithstanding thè wide distribution and individuai abun- 
dance of thè Pulmonata Limnojjhila, there are so few figures 
of thè linguai dentition that it is difiicult to arrivo at a decision 
in regard to thè relations of this singular forin. The following 
are thè cliaracters of thè principal genera which bave been de- 
finitely eliminated; 
Limnaa {stagnalis, 2ycdusti'is). 
Buccal piate arcuate, apex anterior, nearly smooth. Two smooth 
accessory lateral plates. 
Tentacles triangular flattened; eyes sessile on their inner bases. 
Genitalia on thè right side. Poot bluntly rounded bebind. 
Mantle niargin siniple, not extending beyond thè orifice of thè shell. 
Ova deposited in elongate cylindrical masses of jelly, without 
percep tibie envelope. 
Ciisp of centrai tooth siniply pointed, base bilobate. Inner late- 
rals bicuspid, outer ones with more or less numerous notches. 
Shell spirai, turreted, dextral or rarely sinistrai. 
Acella [gracilis). 
