8 



Mr. A. R. Hunt. 



[Apr. 20, 



therefore ripplemarks, occur at much, greater depths thau is commonly 

 supposed. To do this I must prove that there is occasionally motion 

 at the bottom of the sea, and that this motion does not arise from 

 continuous, but from alternate, currents. 



I will commence with a simple case, one that I have studied for many 

 years, viz., Torbay. This bay is an inlet rather more than 4 miles in 

 breadth and over 3 in depth, carved out of Devonian and Triassic 

 rocks of varying degrees of hardness, and open to the south-east. In 

 its centre there is a level area of about 5 square miles, round which a 

 line can be drawn so as to include every 6-fathom sounding and to 

 exclude every other. The bottom over this area consists superficially 

 of a very fine sand, of which a sample taken at any spot will represent 

 the whole. After heavy easterly gales, as has been already stated, the 

 water is very turbid, and the slushy bottom occasionally becomes 

 harder. The level surface of the bottom, the uniformity of its mate- 

 rial, the alteration in its character after gales, and the turbidity of the 

 water, all point to one conclusion, viz., that storm waves materially 

 affect the bed of the bay. To the intensity of this action the fauna 

 also bears witness. Shells that inhabit the 5- and 6-fathom areas, 

 such as Thracia convexa and Gardium aculeatum are occasionally 

 washed ashore from considerable distances. A valve of a full-grown 

 Thracia convexa, picked up on Paignton Sands, was some 3,000 yards 

 distant from the only spot where, to my knowledge, that mollusc has 

 been taken alive in Torbay. Specimens of Gardium aculeatum are 

 occasionally washed ashore and sometimes in vast numbers, but they 

 are invariably denuded of their spines. Even though not washed 

 ashore, thousands are sometimes rolled and killed in the 0-fatkom 

 area, whilst those that survive testify to the severity of the ordeal 

 passed through by the damage done to their shells, and by the repairs 

 effected. The contrast between the old shell denuded of spines and 

 the rim of new growth with spines perfect is often very marked. In 

 one specimen in the museum of the Torquay Natural History Society 

 half the shell is quite smooth and the other half furnished with perfect 

 spines. There are very few genera of molluscs, whether bivalve or 

 univalve, that inhabit the 6-fathom area of Torbay, provided their 

 shells are not internal, whose shells do not occasionally bear upon them 

 the marks of a struggle for existence, more or less severe, with the 

 storm waves of Torbay. 



The marks of damage to which I allude, when severe, cannot be 

 mistaken for lines indicating cessation of growth from change of tem- 

 perature, lack of food, or other such cause; they do not indicate 

 merely a check in the formation of new shell, but in very many cases 

 the destruction of the old. Nor are these marks confined to indi- 

 vidual shells alone, for they are often common to whole colonies 

 together. If a single cardium be found, with the new shell growing 



