Mr. H. G. Seeley on the Pufton 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 j 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.] 



IV. — Remarks on the Potton Sands, in reph/ to Mr. IValker's 

 Paper in the 'Annals of Natural History^ for November 1866. 

 By Harry Govier Seeley, 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 "Gryphaa 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. 



