E. T. Newton — Lemmings, etc. in the Thames Valley. 453 



been discovered. Professor W. Boyd Dawkins and Mr. W. A. Sanford 

 (Brit. Pleist. Mam. Pal. Soc. vol. for 1864, p. xxxvi, 1866) have 

 noticed the occurrence of Arvicola amphibia in the Pleistocene of 

 Ilford, Crayford, and Erith ; while from the last-named locality Mr. 

 E. W. Cheadle (Proc. W. London Sci. Assoc, vol. i. p. 71, 1876) 

 recorded the remains of Spermophilus, which Mr. Lydekker has more 

 recently (Cat. Foss. Mam. Brit. Mus. part i. 1885, p. 212) referred 

 to Falconer's species S. erytlirogenoid.es. 



Several species of small Rodents have been discovered in Pleisto- 

 cene deposits in other parts of England (see Sanford, Quart. Journ. 

 Geol. Soc. vol. xxvi. p. 124, 1869, and Blackmore and Alston, Proc. 

 Zool. Soc. 1874, p. 460), and it seemed likely that they would be 

 found also in similar deposits of the Thames Valley. As no such 

 specimens were to be found in the British Museum, and only one 

 was preserved in the Museum of Practical Geology, I applied 

 to several friends who had made collections from these deposits ; 

 but the result was far from satisfactory. However, Mr. Spurrell 

 and Mr. Cheadle each possessed, in addition to the remains of 

 Spermophilus, some Arvicoline bones, teeth and jaws, and I am 

 under obligation to both my friends for readily placing their 

 specimens in my hands for determination, thus enabling me to 

 record from the Brick-Earth of the Crayford district two species of 

 My odes (Lemmings) and an Arvicola (Vole), not hitherto known to 

 occur in that district. 



The teeth of these Rodents are very characteristic, and the species 

 may therefore be determined with certainty, but the limb-bones 

 cannot so easily be correlated with the teeth. 



Microtus (Arvicola) amphibius, Linn., sp. 



The only specimen from the Brick-Earth of the Tbames Valley 

 which I can with certainty refer to this species is a portion of a 

 lower jaw, from Ilford, in the Cotton Collection, preserved in the 

 Museum of Practical Geology. All the remains of Arvicolidee from 

 Crayford and Erith, which I have seen, are referable to one or other 

 of the species noticed below. 



Microtus (Arvicola) ratticeps, Key and Bl., sp. 



A right ramus of a lower jaw, with two grinders (Fig. 1) in 

 place, together with isolated teeth, from Crayford, in Mr. Cheadle's 

 Collection (now preserved in the Museum of Practical Geology), 

 and three lower jaw rami and several teeth in Mr. Spurrell's 

 Collection, from Erith, are referred to Microtus ratticeps. 



The most characteristic tooth of this species is the anterior grinder 

 of the lower jaw (Fig. 1, m 1), which has five angles on the inner 

 side and three on the outer side, the two anterior and outer columns 

 having coalesced to form one cement space with a nearly flat outer 

 wall. There are differences to be observed, among the specimens 

 from the Thames Valley, in the form of this anterior and outer 

 column, the example figured being rather larger than some of the 

 others, and more nearly resembles the figure given by Messrs. 



