CLASSIFICATION. 15 



it has always been found of a testaceoiis substance ; for these 

 reasons, though we have doubted, we now think that the 

 Bulla hyalina, the Amphisphyra of Loven, may be a true 

 Bulla, 



Bull&a, an undoubted branch of this family, is copiously 

 illustrated in our account of B. aperta, and by recent full de- 

 scriptions of -B. pruinosa, B. catena, and B. punctata, origin- 

 ally-published by us more than twenty years ago, in vol. iii. 

 p. 339 of the Zoological Magazine. 



With respect to the Conovuli it has been said, that except 

 Carychium, they are bisexual. We do not think so, as, be- 

 sides their close connection with the Helices by the respiratory 

 structure, we observed in more than twenty examples of the 

 Pedipes bidentatus that all had well-filled ovaria. We believe 

 they are congressional hermaphrodites ; at least for the present 

 we consign them as members of that reproductive character. 



In consequence of the curious discovery, if it be substan- 

 tiated, which is related in the chapter on the Trochidte, that 

 all the Pectinibranchiata, with circular multispiral opercula, 

 hitherto considered bisexuals, are like the Helices hermaphro- 

 dites with mutual congression, the Trochidte, including the 

 genus Valvata, and the new family of the Vermetidce, con- 

 taining the genera Ccecum and Turritella, are admitted into this 

 division. It seems, however, inexplicable why the strictly 

 circularly operculated Pectinibranchiata should have the ge- 

 nerative system of the Helices, and that all the others, of 

 whatever shape the opercula may be, otherwise than circular, 

 should be bisexuals. 



Though the other hermaphrodites, with mutual congression, 

 as the Limneada, Limacida, and Helicidce, are admitted into 

 our main line, it is impossible to place them therein satis- 

 factorily ; they are an aberrant groiip ; nevertheless they form 

 amongst themselves a closely connective line. The remaining 

 hermaphrodites are the marine Pleurobranchus, Aplysia, Bulla, 

 Bull(ea, and Otina ? These are another aberrant tribe ad- 

 mitted into line, but equally intractable as the last, yet they 

 are pretty closely allied to each other. It appears then, that 

 the general bond of consentaneity between all the families of 



