CLASSIFICATION OF THE TYROGLYPHIM. 43 



At the cephalic end a chitinised fillet with a 



sucker at each end . . 14 Gen. TJRICHOTARSUS. 



No such fillet at the cephalic end . 15 Gen. DERMACARUS. 



This classification is, as might be expected from its 

 author, one of the best ; there are, however, naturally 

 a few points in which I cannot quite agree with it. In 

 the first place there appears to be some error about the 

 genus Rhizogtyphus, due possibly to the author's death 

 before the publication of the work. In the eighth 

 dichotomous division of the classification Dr. Kramer 

 defines his ninth similar division as " fourth leg of 3 

 without suckers." This ninth division includes only 

 the two genera Histiogaster and Rkizoglyphus, but the 

 author seems to have overlooked the fact that the 

 Tifroglyphus crassipvs of Haller,* an American species, 

 has the suckers on the fourth leg of the 3 , and there- 

 fore this mode of differentiation cannot be used for a 

 group which includes the genus. It cannot be that Dr. 

 Kramer considered Haller's species as being a Tyro- 

 glyphux, because when he comes to deal with the genus 

 Mhizoglyphus t he includes Haller's T. crassipes in it, 

 and specifies these very suckers on the fourth leg of 

 the 3 as a reason why he thinks the species must be 

 different from R. echirwpus. Moreover, no acarologist 

 with our present knowledge could doubt that Haller's 

 species is a Rhizoglyphiis. There seems to be a con- 

 fusion about the subject in Dr. Kramer's paper, because 

 in his definition of the genus Bhizoglyphus he states 

 that the anal suckers and those of the legs are present 

 in the 3 ; the anal suckers are present, but the sexual 

 suckers on the fourth leg of the 3 are absent from all 

 known species of the genus except R. crassipes ; and, 

 although the point is not very clearly expressed, yet 

 evidently Dr. Kramer refers to these suckers, because 

 there never are any on any other leg of the Tyrogly- 

 phidse except the fourth; he cannot refer to the 



* " Beschreibnng einiger neuen Milben," in ' Arch. Naturg. L. 

 Jahrg. (1884), p. 218, Taf. xv, fig. 1. 

 t Page 143. 



