72 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IIO 



a veritable rostrum, from the end of which project the movable, 

 laterally toothed digits of the chelicerae. The upper concave surface 

 of the hypostome has a median gutteriike groove (fig. 28 J, K, hg) 

 that leads back to the mouth and is the floor of the food conduit 

 within the rostrum. 



The palps are freely movable on the capitulum. Each consists 

 typically of four segments (fig. 26 A, B), of which the first is a small 

 basal ring, the second and third are long and broad, while the fourth 

 is a small hairy pad or papilla set in a membranous area on the mesal 

 side of the end of the third segment (B, C, G, H). In Dermacentor, 

 however, the apparent basal segment of the palp (C) is immovably 

 united with the second segment, and in Boopliilus (G) a basal seg- 

 ment is not distinguishable from the second. In the females of certain 

 species of Endopalpiger from New Guinea and Australia, Schulze 

 (1935) has shown that the basal segments of the palps are produced 

 into large lobes embracing the rostrum (E, t, t). These segments 

 Schulze regards as the trochanters of the pedipalps, which in other 

 species and in the males of these same species are supposed to be in- 

 corporated in the capitulum, the long third segment of each palp, 

 being interpreted as the usual second and third segments united. A 

 smaller lobe arising from the base of the palp in Ixodes atiritulns 

 Newm. (F, /), however, is regarded by Schulze as pertaining to a 

 secondarily separated proximal ring of the first segment. Superficially, 

 it is not clear that this lobe and the supposed trochanters of Endo- 

 palpiger are not equivalent structures, and it seems strange that free 

 trochanters should be retained only in the females of a few species. 



The chelicerae of the ticks are long shafts deeply buried in the 

 capitulum, or even projecting beyond the capitulum into the body, 

 and each is enclosed in a membranous sleevelike sheath. Distally each 

 chelicera bears a free, strongly toothed segment, or digit, movable 

 by a pair of antagonistic muscles arising in the shaft, and therefore 

 representing the movable finger of a typical chelicera. The digit 

 consists of two principal parts (fig. 26 J, K) ; one is a rigid prolonga- 

 tion (a) from the base of the segment, with a pair of outwardly 

 directed teeth at its apex; the other (b) is a broad lateral lobe with 

 two large teeth, flexibly attached to the side of the fixed process. In 

 Ixodes (I) there is a third, dorsal process, but in some other genera 

 as in Amblyomma (J) and Dermacentor (K, L), a large, thin mem- 

 branous fold (c) arises dorsally from the base of the digit and covers 

 the toothed processes. Finally, the end of the cheliceral shaft is pro- 

 duced into a hoodlike protective lobe (h) on the mesal side of the 

 digit. The digits move in a transverse plane on the ends of the shafts, 



