348 
On thè genus Pompholyx and its Allies, 
These shells forni thè passage froin Physa to Siphonaria. 
Tliey somewhat resemble thè former in their dentition and thè 
lattei’ in their internai anatoiny, tentacles, and raantle-lobe. 
Dr. Gray placed tliein among thè AicricuUdce^ to which there 
is a siipertìcial reseniblance. 
Frolli thè data ahove given, and inforination too lengthy to 
insert bere, I bave drawn thè followino; neneralizations inregard 
to thè arrangement of these molliisks. The forni of thè tenta- 
ciila is a character of minor iinportance, as is also thè position 
of thè genitalia. From thè forni of thè foot and thè biiccal 
plates, with thè characters of thè dentition assisted by those of 
thè anatomy and thè shed, more satisfactory resnlts bave been 
obtained. 
I would propose thè following arrangement : 
ORDER Pri.i?IOI¥ATA. 
SUB-ORDER BaSSOMATOPHORA. 
Group Liìinacea. 
Family LIMNvEIDJE Brod. 1839. 
Air-breathing, biit iisiially fluviatile. 
Foot roiiiided behind. Mouth fiirnished with a transverse buc- 
cal piate, and iisnally with two lateral accéssory plates. Denti- 
tion consisting of a broad radula fiirnished with an inconspiciioiis 
rhachidian tooth, siniple in form ; and niimeroiis nearly nniforin 
lateral teeth which are fiirnished with recnrved cusps, more or 
less dentieiilated ; thè denticiilations being more niimerous and 
thè teeth more compressed toward thè oiiter edge of thè radula. 
Sub-faniily Limn^in^e. Dall. 
Lateral jaws present. 
Rhachidian tooth siraply pointed ; laterals provided with nu- 
merous denticles. 
Tentacles flattened. Genitalia on thè right side. 
