Three neio Parasitic Acari. 433 



The male dexitonymph lias a fairly long and slender poste- 

 rior process or tail, which is furnished with minute denticles 

 resembling those found on the venter. There is a double 

 longitudinal series of scales running along the median line of 

 the dorsal surface as in the generative nymph and larva. 

 Besides this central series there are also numerous scattered 

 scales on the dorsal surface. 



Protonym2:)h. — A smaller nj'raph with a much shorter tail 

 than the male deutonympli also occurs ; presumably it is the 

 protonymphal stage. 



Larva. — The two anterior legs are modified to form clasping- 

 organs, as in the other stages; the third pair of legs is 

 slender and not modified. There is a very short but distinct 

 curved hook-like tail or process at the posterior end of the 

 body. 



Ova. — The eggs are attached singly by one end to a hair 

 of the host ; they are narrow and elongated. 



Material. — Numerous specimens were found on the two 

 guinea-pigs examined. 



Measurements. — Length of ovigerous female 'iG-'Sl ram., 

 of generant nymph "39 mm., of male '35 mm., of male deuto- 

 nvmph (incl. caudal process) '46 mm., of protonymph 

 •31 mm., of larva 243 jw., of ovum 210 //.. Width of ovigerous 

 female 150 fi, of generant nymph 160 fx, of ovum 54 /j,. 



Family Demodecidae. 



Genus Demodex, Owen. 



In his valuable papers * on the genus Demodex Friedrich 

 Gnieiner gives a list of the fourteen described species and 

 also the literature, recording a hundred papers on this subject. 

 Two new forms from the hedgehog and dormouse are described 

 below. 



Demodex muscardint, sp. n. 



? . — This Demodex is a short form and very like that of 

 the house-mouse, but has the capitulum wider as compared 

 with its length. The general shape of the body is also 



* " Demodex follicuhrum des Menschen und der Tiere," Arcli. Dermat. 

 Svpli., Wien, toI. xcii. 1908, pp. 25-96, 4 pis.; "Die Acarus-raiide der 

 Tiere," Zs. Tiermed. Jena, vol. xiii. 1909, pp. 1-32, 81-108, 4 pis. 



Ann (k Mag. N. Hist. Ser. 8. Vol. xx. 29 



