188 Mr. A. Hancock on the Olfactory Apparatus in the Bullida:- 



It will be seen tliat our figure (PI. V. fig. 2) answers quite to 

 this description ; there being a complete want of a proper arti- 

 culation between any of the bones of the arm, hand and fingers ; 

 the arm, and especially the fore-arm, are very broad (the ulna 

 broader than long), the six flat metacarpal bones connected like 

 mosaic in two rows ; and the immoveable fore-fingers arranged 

 like a fan and causing the great breadth of the hand. Cuvier 

 found only one joint in the thumb ; in each of the four succeed- 

 ing fingers four joints, and in the last two. On the specimen 

 brought home there are two bony joints in the thumb, and 

 four in each succeeding finger ; but on each finger a terminal 

 cartilage follows after the last bony joint, containing in the 

 second, a little round bony nucleus. Hence, it is at least very 

 probable, that in a full-grown specimen, the bony joints will be 

 three for the thumb, and five for each remaining finger (on 

 PL V. fig. 2, the cartilaginous nature of the last finger-joint is 

 not particularly expressed). 



[To be continued.] 



XIV. — Observations on the Olfactory Apparatus in the Bullidsb. 

 By Albany Hancock. 



In our paper on the anatomy of Eolis, Dr. Embleton and I en- 

 deavoured to prove that in the nudibranchs the dorsal tentacles 

 are the seat of the sense of smell ; and if this be allowed, there 

 can be little doubt that these organs, in all the other gasteropods, 

 have a like signification. But in the BuUidce, as no tentacles, 

 properly so called, exist, it became a matter of some interest to 

 ascertain if, with the apparent deficiency of these organs, all 

 power of olfaction had ceased to be exercised. Being engaged 

 at present in the investigation of the anatomy of some members 

 of this family, my attention was naturally directed to this point ; 

 and I think I have obtained satisfactory proof that these hornless 

 animals have really the sense of smell highly developed. The 

 head lobe in the Bullida is, in fact, nothing else than the dorsal 

 and labial tentacles fused into one continuous mass. This 

 Cuvier asserted long ago ; and it can very easily be proved on 

 anatomical grounds. In this communication, however, I do not 

 wish to enter at any length on the subject, as I intend at no 

 distant period to give a detailed account of the anatomy of some 

 of these animals. It may therefore suffice at this moment to 

 state, that the nerves which supply the oral and dorsal tentacles 

 in the gasteropods go to this lobe, the former to the anterior, the 

 latter to the posterior portion of it ; — a pretty clear proof of its 

 real nature. 



In Gasteroptero7i the head lobe, or more properly speaking the 



