290 POTAMIDINiE. 



Genus POTAMIDES, Brongniart. 



Shell turreted, whorls angulated or coronated ; aper- 

 ture produced in front into a nearly straight canal ; outer 

 lip thin, sinuated in the middle. 



Sijn. Potamida, Schweigg. Potamidiura, Flem. Po- 

 tomis, Swains. Potamis, Sow.,jun. 



Ex. P. ebeninus, Brugtdere, pi. 30, fig. 6. Opercu- 

 lum, P. ebeninus, fig. 6, «, 6, b. Shell, P. Pacificus, 

 Sowerhy, fig. 6, c. 



The species now existing, most nearly resembling the 

 fossil shells on which this genus is founded, are those 

 we have indicated j they are distinguished by their coro- 

 nated whorls and their rather straight canal. 



Species of Potamides. 



ebeninus, Brug. Pacificus, Sow. 



Lamarckii, VaJcue. 



Genus TYMPANOTONOS, Klein. 



Shell turreted, whorls spinulose or muricated ; aperture 

 round, with a short anterior canal ; columella tortuous ; 

 outer lip thin, sinuated, produced towards the fore part. 



Sgn. Tympanostoma, Sotv. Potamis, Swains. 



Ex. T. fuscatus, LinncBus, pi. 30, fig. 7. Shell, T. 

 fuscatus, fig. 7, a. 



In general appearance, the shells of this genus resemble 

 those of Vihex of Oken, but the twisted columella and 

 distinct canal of the aperture will at once distinguish 

 them. 



