847 



MONOGRAPH OF THE GENUS 

 CE'RITHIUM, Adanson. 



INCLUDING 



Vertagus, Klein, Colina, A. Adams, Bittium, Leach, Pire- 

 nella, Gray, Cerithiopsis, Forbes and Tlanley, Pyrazus, 

 Monlfort, Lampania, Gray, Cerithidea, Swainson, Potami- 

 des, Brongniart, Tympanotomus, Klein, and Telescopium ; 

 Chemnitz. 



Molluscum trachelipodum ; testa turrita, operculifera, varicosa, 

 plerumque tuberculata ct striata ; apertura canalifera. 



In retaining all the species included in this Monograph within 

 a single genus, I am not to be considered as implying an opinion 

 that no divisions could be made with advantage. Many of the 

 genera of authors enumerated above, may probably constitute 

 good foundations for a more accurate distribution of the species. 

 But the misfortune is that the authors have not had the whole 

 range of species before them, or at least have not had to prepare 

 lists of all the species under their respective denominations. Now, 

 it is easy to take two or three species here, and form them into a 

 genus under one name, and to take two or three there to make 

 a genus under another name ; but it is not so easy to take every 

 species and to place each in its appropriate genus. Eor if the 

 species are placed in a line, it is almost impossible to mark 

 the boundaries of the separate groups. I know an instance of a 

 most accomplished conchologist attempting to arrange an exten- 

 sive collection of Cerilhida 1 , according to the modern style of 

 numerous small genera, and the result was, of course, that he had 

 a great many species which he did not know what to do with • 

 and instances occurred in which specimens of the same species 



5 s 



