1 10 Mr. O. Tlioniaa 077 



thoracic widtli. INIale sexual orifice sitnatiMl above the 

 interval between tiie legs of the fir.st ami second pairs. 



JS^ote. — In one male specimen the tracheal tubes leading 

 from fhe capitulmn are quite distinct; each is at first double, 

 but afterwards fuses to t'or-n a single wide lateral main trunk. 



Host : Apodemus sylvaticus. 



Demodex nanus, sp. n. 



? . A minute species very like that present in Sorex vul- 

 garis casteaneus. Length varying from less than 3 up to 

 slightly more than 3^ times tlie width of tlie cephalothorax. 

 Abdomen considerably shorter than combined length of 

 cephalotiiorax and caj)ilulum. Capitulmn usually much wider 

 than long ; the spines on its surface apparently obsolete or 

 absent. 



Total length 87-102 /z. 



Host : the black rat {Rattus rattus)^ a number of specimens 

 coUecled by the author from a freshly killed rat. 



Note. — ilahn has already described a species of Demodex 

 {D. ratti) from a house-rat said to be Miis rattus. I have 

 not been able to consult his original description, which is 

 referred to by Gmeiner. The latter says the species is like 

 that of the dog. From this one would infer that it was an 

 elongated form of comparatively considerable size, similar to 

 that found ill Rattus iwrvecjicas. 



It is probable, indeed, that the rat from which Halm's 

 specimens were taken was really Rattus norvecjicus, the brown 

 or Norwegian rat (syn. Mus decuvianus). It is, of course, 

 l)ossible tluit two species occur in Rattus rattus ^ as is certainly 

 the case in Apodemus sylvaticus. 



XII. — New Sjyecies o/Gerbillus and Taterillus. 

 By Oldfield Thomas. 



(Published by permission of the Trustees of the British Miisenm.) 



Gerhillus allenhyi, sp. n. 



A small species, with short feet and tail j probably allied to 

 G. agag. 



General colour mucli more mouse-grey than the usual tone 

 of gerbils, markedly greyer than G. gerhillus) head, shoulders, 

 and most of the upper surface near " cinnamon-l)uff," but 



