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GENUS APONOMMA 



Eyes wanting. Anal groove surrounds anus pos- 

 teriorly, and opens anteriorly. Anal plates absent. 

 Base of rostrum pentagonal. Scutum covers the 

 dorsum entirely ; usually marked with green spots. 

 Stigmata, comma-shaped. Female, scutum shorter 

 than broad, three green spots. The species are 

 parasitic on reptiles. 



GENUS DERMACENTOR 



Coxa IV very large. Eyes present. Base of 

 rostrum broader than long. Palpi short and thick. 

 Stigmata, comma-shaped. Anal shields absent in 

 male. Coxa I bidentate in <? and ? . Scutum 

 ornamented. About twenty-four species. 



(1) D. electus is the American dog tick. 



(2) D. occidentalis conveys ' spotted fever ' of 

 the Rocky mountains, the cause of this disease being, 

 however, unknown. 



GENUS ORNITHODOROS 



Eyes present or absent. Rostrum hidden under 

 a projecting beak (head) close to the margin of the 

 body so that the tips of the palpi only are visible from 

 above. Body generally oval, sides generally straight, 

 skin mammillated throughout. Lateral margin not 

 different as in Argas. No moveable plate on each 

 side of palpi. 



(i) O. savignyi. Has two pairs of eyes situate 

 on a horse-shoe shaped elevation surrounding the 

 base of the legs and the mouth parts. Hind tarsi are 

 slenderer than in O. moubata. On the last segment 

 of the hind legs are 'three knobs, the distance between 

 the second and third three times as great as that 



