ONCHIDIUM. 5 



from the other Pidmonifera, in the same manner as the 

 0])istJiohrancMata do from the ProsohrancMata, so far, 

 at least, as the relative position of these organs is con- 

 cerned. And, moreover, it is worthy of remark, that 

 in OncJiidium the anal orifice is distinct from that of 

 the lung, and that in Arion and Helix the excretory 

 apertui'es are within the pulmonary arch. The true 

 signification of these facts can scarcely at present be 

 determined; more information is required respecting On- 

 chidium and its allies, to throw additional light upon 

 the subject." 



