22 ARKIV FÖR ZOOLOGI. BAND 7. NIO 28. 



resting position. Furthermore tbe dorsal shield is very härd 

 and armour-like and when tlie coxae I are shut up and 

 tlie legs laid together they animals do not offer any protrud- 

 ing points to an attacking foe. 



All these features are secondary adaptations. A few of 

 tlie Uropodince have however, beside the position of tbe male 

 genital aperture, still anotber comparatively j)rimitive fea- 

 ture, tbat tbe fusion of tbe dorsal sbields is not completed, 

 as in Uropoda foraniinifera Tgdh., wbere a small posterior 

 sbield remains. 



If tbus on tbe otber band tbe Uropodince, in spite of some 

 primitive features, as a wbole are too modified to be reckoned 

 amongst tbe most primitive of tbe Parasitidce, and tbe sub- 

 families Parasitmce, Dermanyssinoe, Celcenopsince and Lcelaptince 

 on account of tbe complicated secondary sexual cbaracters 

 cannot be taken into consideration, we will bave to examine 

 tbe otber subfamilies, e. g. Zercormice, AiitennopJiorinGe, Hetero- 

 zerconince and Ehodacarince.^ 



Of tbese tbe Heterozerconince are too imperfectly known, 

 as only one sexe of a single species is known, to be treated 

 bear. It bas, bowever, a single dorsal sbield and specialized 

 mandibles, botb not primitive cbaracteristics. 



Tbe AntennopJiorince are upon tbe wbole in several re- 

 spects bigbtly modified (sbape of body and gnathosoma). It 

 is, bowever, remarkable, tbat one species Parantennulus scolo- 

 pendrarum Berl. bas a pair of small, free dorsal sbields be- 

 hind tbe large one, wbicb is a primitive feature. Anotber 

 species Paramegistus conjrater Tgdh bas a pair of jugular 

 sbields (compare p. 20). 



Tbere remains consequently tbe Zerconince and the Rhoda- 

 carinoe and in some genera of tbis group we find, as I will 

 endevour to prove, the greatest number of primitive features. 



In the Zerconince tbe genus Epicrius is bowever to modi- 

 fied to be taken into consideration (prolongation of legs I, 

 and loss of ambulacres on these, sexual difference between the 

 mandibles and single dorsal shield); it possess, on the otber 

 hand, a feature wbicb is probably primitive, no peritremata. 



Tbere remain tbus tbe two genera Zercon and Sejus. 

 In botb tbese the mandibles as well as the hypostoma are 



^ The Holothyridce I consider as a very distinct group, not to be 

 classed amongst the Parasitidce. 



