346 
On thè genus Pomi:»ÌLolyx and its AlUes, 
relations with Pompholyx ave veiy dose. Many small embvy- 
oiiic shells weve found in thè dried reraains of thè animai. 
Physa {fontinalis, heterostroplicC) . 
Buccal jjlate chevron-shaped or tviangiilar witli thè siiles excavated ; 
strongly striate, apex posterior ; occasionally menibrauons or absent. 
No accessory plates. 
Tentacnla filiform, long, with a small basai anricle. Eyes at thè 
front of thè head, near or on thè inner bases of thè tentacles. 
Genitalia on thè left side. Foot acutely j^ointed behind. 
Mautle edge digitate or lobed, extending partly over thè shell. 
Teeth {Physa humerosa Gld. Arizona) alternate, differing vddely 
froin those of lÀmncea. Central tooth wide. Base with projecting 
processes before and behind. Cnsp Consolidated with thè base, quin- 
qnedentate. Laterals alternate. Principals strong, obhquely bent, 
conib-like, 96 in a row on each side. Secondaries, narrow, oblong, 
anteriorly depressed with a simple roiinded cusp. Insertion between 
thè principals. From their extreme tenuity these secondary teeth 
are liable to be overlooked. They are omitted in all thè figures of 
thè teeth of Physa, accessible to me. 
Ova deposited in flattened OA'al masses, wnthout perceptible covering 
except of jelly-like mucus. 
Shell sinistrai, turreted, edge continuous. 
Pulinus (liypnorum). 
Jaw strongly arcuated, thin, cartilaginous. No accessory plates. 
Tentacles slender, long, filiform. Eyes sessile on a slight expansion 
of their inner bases. 
Genitalia on thè left side. Foot acutely pointed behind. 
Mantle edge simple, not extending beyond thè shell. 
*Teeth strongly resemble those of Physa ; centrals broad, base bifio 
before and behind. Shell elongate, sinistrally spirai, margin entire. 
Ova capsules ovate cylindiùcal, without membranous envelope. 
* Bulinus nitens, Phil. , Lake Nicaragua. 
