20 EOCENE MOLLUSCA. 



of that division involves the distribution of the genera forming Professor Owen's 

 extensive family Teuthida between the two groups, and the characters on which 

 M. d'Orbigny has formed his families are at the least of equal importance with those 

 used by Professor Owen, I have adopted the classification proposed by M. d'Orbigny, 

 but with the following modification. That author has placed Beloptera and Spirulirostra 

 among the Spirulidce. Now the shells of these genera present a series of siphonated 

 air-chambers associated with a rostrum, and therefore bear a much closer affinity with 

 Belemnite than with the shell of the recent Spirilla. I have, therefore, placed them, 

 as well as Belemnosis, among the Belemnitidm ; and as I agree with Voltz in considering 

 Belosepia to have possessed a camerated and siphoniferous shell, I have also placed 

 that genus in the same family, notwithstanding the close affinity between its remains 

 and the internal shell of the recent Sepia. 



