TO GEOLOGY. 167 



Observations. This is a much smaller species than the 

 last, and its sharp transverse striae, which are much more 

 distant, together with the folded columella, render it im- 

 possible to confound them. 



T. venusta. Plate 5. Fig. 173. 



Description. Shell subulate, very much attenuated, 

 with close longitudinal ribs and minute transverse striae in 

 the intermediate spaces ; substance of the shell thin ; 

 spire very much elevated, acutely pointed ; suture linear ; 

 whorls fifteen, flattened ; mouth narrow ; columella smooth ; 

 outer lip . 



Length 13-20ths, Breadth 3-20ths, of an inch. 



Observations. A very distinct species from the above, 

 being more attenuate, having a smooth columella, and 

 being more closely ribbed. The transverse striae, inter- 

 mediate between the ribs, are very minute, while in the 

 above two species they are larger and cross the ribs. 



Four species of this genus have been observed in Eng- 

 land : three species in the Oolitic Group and one in the 

 London Clay. Sixteen are given for the Tertiary by M. 

 Deshayes. Ten of these are found at Baden (Miocene), 

 and seven at Bourdeaux (Miocene). In the Tertiary of 

 Maryland Mr Conrad has observed one species, which he 

 calls simplex, being the only one heretofore observed in our 

 Formations. 



