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assumes generally on the dorsal surface a hardened, chitinous, 

 more or less smooth and darker appearance. Near the margin 

 of the lateral and posterior sides the dorsum is impressed by a 

 deep line, leaving a distinct rim around the whole body. This 

 rim is in its posterior region divided, by eleven lines, into thirteen 

 distinct lobes. 



But we notice in the females of two genera a striking deviation 

 from this character, for here, in Ixodesand Boophilus, the integu 

 ment of the dorsal surface is not more hardened, chitinous, or 

 darker than on the underside. The lateral rim and posterior 

 lobes are absent or only faintly indicated, and the whole body is 

 covered uniformly by more membraneous, coriaceous tegument, 

 in consequence of which the sides are more rounded and the body 

 more cylindrical than in the other genera. 



The body of the adult female is differentiated at once from the 

 male by the prominent dorsal shield which we have observed in 

 all the inferior forms and which is here retained only in the ma 

 ture female, while it has disappeared as such in the male, where 

 it, in fact, extends over the whole surface. 



This dorsal shield surrounds more or less that excavation 

 of the body in which the capitulum is inserted ; its size, form, and 

 structure vary in the different species, but it is generally of an 

 ovate or lozenge-like form, longer than broad, and its anterior 

 border is either not broader than the base of the excavation, or 

 it is so broad that it covers the whole anterior part of the body to 

 its external margin. The former is the case in Ixodes, while the 

 latter occurs in Amblyomma and Hyalomma. In Dermacentor it 

 extends to the two anterior sharp projections between which the 

 capitulum lies, but here the shield does not reach the margin of 

 the body. The shield in its extension backward becomes broader 

 to about the middle of its length, whence it attenuates to the pos 

 terior end. The surface of the shield is marked with round pin- 

 like, larger or smaller impressions, which are generally more fre 

 quent and of a larger size in the anterior region. 



Two impressed lines, more or less distinct, starting from the 

 lateral sides of the excavation and running backward in various 

 shapes, divide the surface of the shield into three parts the middle 

 and two external wing-like portions. The median part is often 

 considerably swollen or arched in its anterior area, while the 



