^•^'•'1 Field Naturalists' Club — Proceedings. 91 



EXHIBITS. 



By Mr. J. W. Audas, F.L.S. — Haloragis rubra, Schindl., Red 

 Raspwort, collected by Mr. Smith at Sunbury, 15/6/18. 



By Miss A. Fuller. — Orchids collected during the excursion 

 to Black Rock. 



By Mr. C. J. Gabriel. — Marine shells — Chlamys leopard us, 

 Rve., from North- West Australia ; C. pallium , Linn., from 

 Maiden Island ; Chlamys plica, var. flabclloides, Rve., from 

 Japan. 



By Mr. F. Keep. — Acacia prominens and A. fimbricata, for 

 comparison. 



By Mr. P. Crosbie Morrison. — ^Water-beetles of the families 

 Dytiscidae and Gyrenidse. 



By Mr. A. L. Scott. — Zeolites from Giant's Causeway, 

 Ireland, between crossed nicols. 



By Mr. H. B. Williamson. — Grevillea Williamsoni, F. v. M., 

 collected in Grampians, October, 1893. 



After the usual conversazione the meeting terminated. 



TRACKS OF GARDEN SNAIL. 



By Thos. Steel, F.L.S. 



(Communicated by E. S. Anthony.) 



(Read before the Field Naturalists' Club of Victoria, 8th July, 191 8.) 



In the Victorian Naturalist for March last (vol. xxxiv., p. 171) 

 Professor Baldwin Spencer asks for information regarding the 

 track left by the common introduced garden snail. Helix aspera, 

 which is in the form of a series of short, thick, detached lines 

 or patches. I have made a number of observations on the 

 subject, and think I have arrived at the correct explanation. 



The mucus which forms the track appears to be discharged 

 intermittingly from the orifice of the large mucus gland near 

 the anterior end of the ventral surface, and its purpose is to 

 serve as a lubricant for the smooth passage of the animal's 

 body. As the animal moves forward the mucus is thus deposited 

 in isolated portions, with the result that on a rough surface, 

 such as asphalt, most of the mucus remains where deposited, 

 and is not spread forward to any extent. On a smooth surface, 

 such as glass, the mucus is carried forward, through the animal's 

 ambulacral surface being in close contact with the glass, and so 

 a continuous trail is formed. When snails crawl on rough 

 surfaces, such as asphalt, wood, or a hard earth footpath, the 

 mucus is frequently carried across from one deposit to another 

 in the form either of a thin film or a mere thread, thus forming 



