336 On thi genu* Pompholyx <in<l its Allies', 



# 



effusa. I propose, therefore, to indicate the species BsJPompholyx 

 /. ma, ear, solida, until more definite information be ob- 

 tainable. 



There can be do doubt that the anatomy of two such closely 

 allied forme must be nearly identical, and there are probably no 

 differences in the soft parts alone (except in the dentition of the 

 outer laterals) by which the two species might be separated. 



A careful examination of some 30 specimens from among 

 those sent by Mr. Harford from Clear Lake have afforded the 

 following notes. 



External parts.. The general accuracy of outline of the 

 figure given (in the Proc. CaL Acad. L866, p. 268) is fully con- 

 firmed. No tentacular eyes are present The foot is short, 

 (about twice as long as broad), posterior extremity bluntly 

 rounded as in Planorbis. The veil, or lips, are broad and 

 semilunar. The mouth is minute and rounded-transverse. 



The tentacles are rather short, Btoul and slightly larger at the 

 tips than more posteriorly. They are marked by a central line 



of pigment cells which accompany the tentacular nerve, and in 

 some individuals, near the tips, an aggregation of these pigment 

 cells, forming a black patch or dot, was observed. This is un- 

 questionably what was taken for a BOCOnd pair of even by Mr. 



Gabb. In other individuals, however, the pigmentary deposil 

 was oearly or entirely absent, and the tips of the tentacle.- were 

 of a pale yellowish color. The colors, as far as could be deter- 

 minedfrom the specimens in glycerine, were as represented in 

 the paper alluded to. The true eyes are aessileoo the front of 



the head. near, hut not on. the inner l»a-e> of the tentacle.-. 



Nervous system. The oesophagus is surrounded by a ner- 

 vous collar, with one large and one Bmall ganglion, the latter 

 above and the former below the throat. These ganglia arc 



really composed of pair-. \cry closely united to each other. 



Prom the lower one the tentacular and tl ptic oerves are 



it Nervous branches radiate from the ganglia, bul were 

 minute to be satisfactorily traced to their terminations. 



