136 [Dec, 1846. 



Annual Meeting, Dec. 29, 1846. 

 Vice President Wetherill in the Chair. 

 The Committee on the following communication by Dr. 

 Leidy, reported in favor of publication. 



On the situation of the Olfactory sense in the terrestrial tribe of 

 the Gasterojoodous Mollusca. 



By Joseph Leidy, M. D. 



While no observer of the habits of the terrestrial Gasteropoda 

 doubts the existence of the sense of smell in them, but on the con- 

 trary, asserts positively that it does exist, the anatomist heretofore 

 has not been able to point out its precise seat. 



Swatnmerdam, in his Biblia Natura, speaks decidedly of the ex- 

 istence of this sense in the Helix pomatia, but offers no conjec- 

 ture as to its situation. Blumenbach remarks, under the head of 

 Vermes, " Several animals of this class appear to have the sense 

 of smelling, as many land snails (Helix pomatia, &c.,)" and after- 

 wards adds, " But the organ of this sense is hitherto unknown ; 

 perhaps it may be the stigma thoracicum." Cuvier in his Memoir 

 sur la Limace et le Colimacon, after remarking the delicacy of this 

 sense, thinks it probable it may reside " Dans la pean toute en- 

 tiere, qui a beaucoup texture d'une membrane pituitaire." 



In investigating the anatomy of this tribe of Gasteropodous 

 Mollusca, I detected an organ which appeared to have been en- 

 tirely neglected, or has escaped the notice of those who have dis- 

 sected these animals. It is a depression or cul-de-sac, having its 

 orifice beneath the mouth, between the inferior lip and the ante- 

 rior extremity of the podal disk, and which in many species of dif- 

 ferent genera is elongated backwards into a blind duct, more or 

 less deep, occupying a situation just above the podal disk, within 

 the visceral cavity. In Bulimus fasciatus it extends backwards 

 as far as the tail, and is several times folded upon itself; in Glandina 

 truncata it extends the length of the podal disk ; in the various species 

 of Helix it is found from a superficial depression to a sac the length 

 of the podal disk; in Succioea obliqua it is of considerable length; 

 in Limax and Arion it is a superficial depression : in an undeter- 

 mined species of Vaginula, hereafter to be described, I found it 

 half an inch in length, &c. 



It is composed of two laminae ; a delicate lining mucous mem- 

 brane and an external layer, having a whitish or reddish glan- 

 dular appearance. A large nerve, on each side, from the suboeso- 

 phageal ganglia, is distributed to its commencement, besides 

 which it receives numerous smaller branches along its course 

 from the same ganglia. Its arterial supply is derived from the 

 cephalic branch of the aorta. 



