164 Rev. R. SHEPPARD’s Account 
middle and perfectly straight; in the latter it is also four-sided 
in the middle, but curved as in H. aspersa. The Spicula of the 
plain sort I have not been fortunate enough to find ; but as they 
differ in the two former, it is reasonable to suppose they do also 
in this. 
Now to my reasons for considering the three sorts as distinct 
species, a seemingly decisive argument has been objected, viz. 
that they have all been produced from one deposit of eggs. But 
has it ever been clearly ascertained that such deposit was made 
by a single snail ? 
Being on the subject of H. nemoralis, the following passage 
from Shaw's Travels in Barbary will not I hope be deemed irre- 
levant; because something similar has been observed in this 
part of the country by me, tending even to establish (if any thing 
were wanting) the truth of what that eminent writer advances. 
“ Those parts of the Sahara,” says he, ** which these birds 
(Ostriches) chiefly frequent, are destitute of all manner of food 
and herbage, except it be some few tufts of coarse grass, or else 
a few other solitary plants of the Laureola, Apocynum, and some 
other kinds, each of which is equally destitute of nourishment, 
and in the Psalmist's phrase, cxxix. 6. even withereth afore it be 
plucked up. Yet these herbs, notwithstanding this dryness and 
want of moisture in their temperature, will sometimes have 
both their leaves and their stalks studded all over with a great 
variety of Land-snails, which may afford them some little nou- 
rishment." 
In like manner, parva componere magnis, on that sandy com- 
mon at Stony-Point, in Walton in the Naze, above mentioned, 
the only food which the numerous Helices there found can meet 
with, consists of a few* tufts of hard coarse grass, occasionally 
* This was particularly the case in the year 1819. There was much more grass late in 
the spring of 1821, in consequence of the frequent rains which had fallen. — le 
mter- 
