1882.] J. Wood-^iison— St nicture of" Foot" in Fuhnonata. 61 



technical name for it appears to exist in the English language, he proposes 

 to call i\\Q peripodium in allusion to its relation of position to the locomotor 

 ventral surface or foot of the mollusks possessing it, but which he thinks may 

 be homologous with the lateral folds (epipodia) of many marine mollusks 

 (Hnliotls, e. g ) Very frequently the peripodiura is provided at its posterior 

 extremity witli a capacious pit, the capacity of which may be increased by the 

 prolongation upwards of its anterior margin in the form of a horn, which 

 not being specially sensitive is not a tentacle ; often it is without this termi- 

 nal pit ; it is invariably richly ciliated throughout from the mouth on one 

 side round to the mouth again on the other side dorsally ; equally invariably is 

 it limited off from the side of the body (and very frequently also from the 

 muscular foot) by a peripheral groove, which deepens anteriorly. Its office 

 is to assist in lubricating the foot, the pit when present receiving the 

 effete lubricating fluid and throwing it off in gelatinous lumps. 



The foot-gland, as is well known, pours out its abundant and constantly 

 flowing secretion through an aperture which is situated below and a little 

 behind the mouth into a hollow whence it naturally fall into the deep 

 • anterior end of the dorsal peripheral groove, whence again it is carried by 

 the cilia with which the surface of the peripodium is beset (being distri- 

 buted to the foot as it goes) to the terminal pit. In those forms in which 

 this pit does not exist, the secretion that has subserved lubrication is 

 merely left behind by the crawling mollusk. 



As Pulmonata possessing a ciliated peripodium with and without a 

 terminal pit were to be found in every quarter of the globe, and as it was 

 in the highest degree improbable that so highly specialized a structure 

 subserving such an important purpose in the animal economy as this evident- 

 ly did had arisen independently many times in many different forms in 

 many widely separated areas of the earth's surface, he considered that it 

 had a higher taxonomic value than had hitherto been assigned to it, and he 

 felt strongly inclined to distinguish those forms that possessed it and those 

 that did not (or had lost it) from one another by calling them Cbaspedo- 

 PHOEA and LiPOCRASPEDA respectively. 



Order PULMONATA. 



Suborder STYLOMMATOPHORA. 



CRASPEDOPHOHA. 



Peripodial pit 'present. 

 Arion. Nanina. Macroceras, 



Geomalacus. Microcystis. JCenta, 



Dendrolimax. Macrochlamys. Fhysota. 



Cryptosoma. bitala. Ventridens. 



