Mr. H. G. Seley on the Potton Sands. 23 
abdomen the appearance of a double row of tessellation on each 
side of the middle; the outer mark is bilobed, the lobes point- 
ing backwards; the inner mark is more or less triangular, the 
apex pointing backwards. In none of my specimens is there any 
appearance of the fossette which Erichson uses as a character to 
divide the genus into two sections, according as the males have 
a fossette on the fourth segment or on the third and fourth 
segments of the abdomen. 
The species is otherwise not difficult to distinguish. Its 
upper surface being concolorous reduces the number with which 
to compare it to a few; the ordinary proportions between the 
elytra and the thorax remove it from the Chilian species; and 
the double tessellation of the pubescence on each side of the 
abdomen distinguishes it from the Australian, Natal, and 
Siberian species. 
If we except one or two of the species which are established 
and go everywhere in ships, the members of this genus do 
not appear to be so cosmopolitan as is generally supposed. At 
any rate, the other species come constantly from the countries 
to which they are ascribed. 
- [To be continued. ] 
1V.—Remarks on the Potton Sands, in reply to Mr. Walker’s 
Paper in the ‘Annals of Natural History’ for November 1866. 
By Harry Govier Seerey, F.G.S., of the Woodwardian 
Museum in the University of Cambridge. 
In July 1866 I wrote to the editors of this Magazine a letter on 
the fossils of the sands at Potton, expressing a few results of 
investigations into the nature of the sands between the Kim- — 
meridge Clay and what are usually called the Middle Cretaceous 
beds*. My friend Mr. Walker, apparently misunderstanding 
my paper, and being zealous for the geological honour of our 
University, at once wrote a refutation of my mistakes, and pub- 
lished it in various sections of the British Association and in 
this Magazine. However, the only mistake in my letter was the 
statement that “Gryphea dilatata is perversely wanting,” which, 
indeed was then true; for before the end of July it occurred in 
great plenty, and was exhibited in the Woodwardian Museum. 
* A portion of my results were given in a paper “On the Carstone 
and its Southern Extension,” read in the Geological Section of the British 
Association at Nottingham; and the whole of them, with the method on 
which they depended, were given in a paper “ On the Potton Sands,” read 
before the Cambridge Philosophical Society, Nov. 12, 1866. 
