I XO DO IDEA ' 695 



marked out by grooves lying along the posterior margin of the 



body between the stigmata. 

 {e) The dorsal g'rooves are usually longitudinal, and not always distinct, 



as they are due to muscular contractions, 

 if) Pits, ,hairs, spines, etc., may be visible on the dorsal surface. 



2. Ventral Surface. — The ventral surface exhibits (Fig. 324): — 



{a) The genital pore, situated in the ventro-median line, between the 



coxae of the first three pairs of legs. 

 (6) The anus, situate in the ventro-median line, behind the posterior 



pair of legs. It is surrounded by a valve, and in the male of 



certain genera has laterally the clypea or anal valves, 

 (c) The ventral shields of chitin are small sclerites covering the surface 



in the male. 



Fig. 311. — Dorsal View of the Capitulum Fig. 312. — Chelicera 

 OF A Tick: Female {HcBmaphysalis punctata of H . punctata : Male 



C. andF.). (C. and F.). 



I, Chelicerae; 2, hypostome; 3, palp; 4, porose area. 



(After Nuttall, Cooper, and Robinson, Journal of Parasitology.) 



{d) The stigmata lie one on each side of the body, between the 3rd 

 and 4th pairs of legs in the Argasidae, and behind the fourth 

 in the Ixodidse. 



{e) There are often to be seen a pair of genital furrows and an anal 

 furrow. 



(j) Pits, pores, hairs, and punctations are to be found as on the dorsal 

 surface. 



3. Anterior Margin. — This varies as compared with the posterior, being 

 sometimes straighter, sometimes emarginate, and receiving at the camero- 

 some the rostrum. 



4. Posterior Margin. — This is generally rounded, and often marked by the 

 festoons already mentioned on the dorsal surface. 



5. Lateral Margins. — They vary as to their straightness or degree of cur- 

 vature. 



