107 
Mr. David Davies and Mr. Jordan spoke of having heard from the 
officers of one of H.M.'s vessels, who had been taking soundings in the 
Bristol Channel, that great changes of level were in progress there, some 
channels being gradually blocked up, or made more shallow, and others 
becoming considerably deeper. 
Mr. S. H. Swayne referred to the accumulations of sand on hill-tops, 
as instanced by the castle at Oxwich Bay, Gower, which was built on the 
top of a hill, and partly buried in sand. 
The Vice-President in concluding the discussion, referred to the 
existence of vast sandy plains in central Asia, in Prussia, near Arnheim, 
and many other places. When this enormous quantity of sand was taken 
into consideration, as well as the high winds that occasionally prevailed, 
these accumulations were not to be wondered at. His thoughts were 
naturally carried back to Egypt, where whole towns were buried in sand, 
and utterly forgotten. The constant movement of sand there accounted 
for the frequent re-discovery of monuments and temples, such as those at 
Memphis and Ipsambool, at intervals of years, the accounts of former dis- 
coveries having been forgotten. 
Mr. Thomas Graham Ponton then read the following paper on 
" The Alimentary System of Tegenaria civilis (one of the house-spiders)." 
Tegenaria civilis, the anatomy of whose alimentary system I am about to 
describe, belongs, as do all the animals popularly called " Spiders," to the Fam- 
ily Araneidse of the Arachnida Filosa, or Pulmonaria. 
Although all my observations will refer particularly to the species I ha, 2 chosen 
for illustration, many of them might with propriety be applied to any other 
member of the Araneidse. 
In such a large family as this, however, there are in every genus minute 
differences of structure, the description of which would far exceed the limits of 
a single short paper. I have, therefore, thought it better to confine myself to one 
in particular, in place of trying to take a cursory view of the whole. 
I chose the Tegenaria civilis as the basis of my remarks for several reasons, but 
chiefly, because it is a very common, if not the most abundant, of our British 
Spiders, and there must be few of those who hear me to-night, who have not 
seen it lurking in its web, when they were moving some old articles of furniture, 
or visiting some remote garret or lumber rooms, and have thus acquired a know- 
ledge of its general appearance at least. 
The term alimentary system, I have employed in its widest sense, including 
in it all organs, directly or indirectly subservient to the nourishment of the 
animal; such for instance as the spinnerets from which are eliminated those 
wonderful webs in which the spider snares its prey. With these few words of 
preface, I will now proceed with the immediate subject of my paper, and commence 
by describing what are called the falces. The " falces " are a pair of jaw-like 
organs, situated immediately above the mouth, they are attached to the fore part 
of the cephalo -thorax by a joint, and have a lateral motion like the jaws of insects. 
These organs perform somewhat the office of mandibles, and have in fact been 
thus called by some authors, but improperly so, for they form no part of the 
mouth. 
