348 On the genus Pompholyx and its Allies, 



These shells form the passage from Physa to Siphonaria. 

 They somewhat resemble the former in their dentition and the 

 latter in their internal anatomy, tentacles, and mantle-lobe. 

 Dr. Gray placed them among the Aurieulidiv, to which there 

 is a superficial resemblance. 



From the data above given, and information too lengthy to 

 insert here. I have drawn the following generalizations in regard 

 to the arrangement of these mollusks. The form of the tenta- 

 cula is a character of minor importance, as is also the position 

 of the genitalia. From the form of the foot and the buccal 

 plates, with the characters of the dentition assisted by those of 

 the anatomy and the shell, more satisfactory results have been 

 obtained. 



I would propose the following arrangement: 

 ORDER PULMONATA. 



Sub-order Bassomatophora. 

 Group Limn ace a. 



Family LIMN^EIDJC Brod. 1839. 



Air-breathing, but usually lluviatile. 



Foot rounded behind. Mouth furnished with a transverse buc- 

 cal plate, and usually with two lateral accessory plates. Denti- 

 tion consisting of a broad radula furnished with an inconspicuous 

 rhachidiai] tooth, simple in form; and numerous nearly uniform 

 Lateral teeth which are furnished with recurved cusps, more or 

 denticulated ; the denticulationa being more numerous and 

 the teeth more compressed toward the outer edge of the radula. 



Bub-family Limn. kink. Dall. 

 Lateral jaWS present. 



Ethachidian tooth simply pointed; laterals provided with nu- 

 merous denticles. 

 Tentacles flattened. Genitalia on the right side. 



