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CONCHOLOGY. 



Turritella duplicata 

 T. terebra. 

 T. imbricata. 

 T. replicata. 

 T. fuscata. 

 T. cornea. 



Turritella brevialis. 

 T. bicingulata. 

 T. trisulcata. 

 T. exoleta. 

 T. carinifera. 

 T. Australis. 

 T. Virginiana. 

 The twice-girdled Turritella 



PI. 24, 



T. bicingulata. 

 fig. 5. 



Species that answers to the above description. 



T. terebra. The auger Turritella. 



Taper, pointed, acute transverse striae, the intermediate 

 spaces prominent and acute ; white, reddish, or cream col- 

 oured. 



FAMILY XVI. 



Canalifera. Eleven genera. 



1. Cerithium. Thirty-six species. 



A beautiful and numerous genus of turreted shells, with 

 an expanded outer lip and short beak ; the greater part are 

 marine ; many are found at the mouths of rivers, and a few 

 in lakes, though none can properly be called river shells. In 

 appearance they are like an elongated pyramidal cone, and 

 the spire is at least two thirds the length of the shell. The 

 exterior is seldom smooth, but striated, tuberculated, granu- 

 lated, or spinous. 



Shell more or less turreted, generally tuberculated ; aper- 

 ture small, oval, oblique ; the columellar edge hollowed, cal- 

 lous; the right edge sharp, and dilating a little with age; 

 operculum horny, oval, rounded, sub-spiral, and striated. 



Cerithium giganteum. Cerithium erythraeonense. 



C. palustre. C. muricatum. 



C. sulcatum. C. radula. 



C. telescopium. C. crassum. 



C. ebeninum. C. decollatum. 



