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MR. STANLEY HIRST ON 



Family L i s t r o r h o r i d je. 



Listrophorus frontalis, sp. n. (Text- fig. 10 A & B.) 



<S . Dorsal (frontal) process of capitulum much more strongly 

 salient than in L. argentinus, being fairly long and conical (text- 

 fig. 10 A). Abdominal lobes rather shorter than in L. argentirms, 

 and somewhat differently shaped (text-fig. 10 B). 



5 . Process of capitulum similar to that in the male. 



Length, 6 330-345 /*, $ 365 /x. 



Habitat. Parasitic on the rodent Orizomys delticola, from Isla 

 Ella del Delta, Parana. 



Text -figure 10. 



A. Anterior end of Listrophorus frontalis. B. Posterior end of abdomen of male of 

 the same species. C. Anterior end of ListropJiorus argentinus. D. Posterior 

 end of abdomen of male of this mite. 



Listrophorus argentinus, sp. n. (Text-fig. 10 C & D.) 



S . Dorsal (frontal) process wider than long and rounded in 

 outline (text-fig. 10 C). Abdominal lobes ending in a delicate, 

 almost truncate process, the posterior edge being, however, 

 slightly oblique ; the gap between the two lobes long and 

 narrow (text-fig. 10 D). 



5 . Capitulum of female very like that of the male. 



Length, 6 345-360 /*, $ 415-450 /x. 



Habitat. Argentina; on a rodent (Scapteromys tomentosus) . 



Trichcecius brevipes Can. & Trt. 



According to Canestrini and Kramer in ' Das Tierreich ' (Sar- 

 coptidee, etc.), this interesting little Listrophorid mite has only 

 been found in Thessaly, and I cannot find a later reference to the 

 species. As a matter of fact, it is not uncommon on English 

 rodents. I have collected numerous specimens off Evotomys 

 glareohis britannicm at Exeter, and off Microtus agrestis at 

 Barnes, Surrey. 



