26 
Argas persimis 
attracted the notice of the majority of observers of this species. They 
are di.sposed in a regular conformation, but there is frequently some 
slight asymmetry of arrangement between the right and left halves of 
the body. These discs, as was first observed by Heller (1858), mark the 
sites of insertion of the body-muscles and are strictly homologous with 
the grooves which form a consjiicuous feature of the superficial anatomy 
of the Ixodidae. They are quite visible to the naked eye, particularly 
in gorged individuals, where, owing to the distension of the body, they 
appear as deep pit-like depressions, the attached muscles having 
prevented the expansion of the body at these points. 
Towards the anterior extremity of the ventral surface, snugly en¬ 
sconced in a deep depre.ssion termed the camerostome {cam.), is the 
capitulum {cap.). The capitulum is comprised of a basal portion—the 
basis capitidi (see PL IV, fig. 8, b.c.), upon which are borne the first and 
second pairs of appendages—the chelicerae and the palps {ch. and p.). 
The oral opening is situated on the capitulum but is concealed from 
the ventral aspect by the hypostome {h .)—a median prolongation of the 
basis capituli. The chelicerae are situated above, and the palps on 
either side of the mouth. The proximal portion of the basis capituli 
is partially telescoped into a large, obliquely inclined opening, the 
capitular foramen, in the ventral body wall, and is articulated with the 
body in such a manner as to allow free movement in the sagittal plane. 
In the resting state, the capitulum is maintained in a position of 
extension, being depressed into the cavity of the camerostome. 
The camerostome (see PI. Ill, fig. 7, cam.) is approximately rect¬ 
angular in shape, and its lateral walls are raised into a pair of salient 
integumental folds, the camerostomal folds {cam.f.) which originate 
some distance posterior to the basis capituli. These camerostomal folds 
protect the retracted capitulum, on either side of which they run for¬ 
wards, to terminate at the antero-lateral angles of the camerostome. 
The four pairs of legs {1. i, ii, Hi and iv) are situated on the anterior- 
half of the ventral surface, the coxae of the 1st pair lying immediately 
external to the posterior half of the camerostomal folds. With the 
exception of a narrow interspace between the 1st and 2nd pairs, all the 
coxae are contiguous. They are firmly articulated to the ventral body 
wall, but are capable of a certain amount of movement—abduction and 
adduction. This mobility of the coxae is rendered possible by the fact 
that the body wall is raised into two prominent longitudinal folds. 
The outer or supracoxal fold {s.cx.f.) runs along the external margins 
of the coxae, curving inwards in front ot coxa I, and merges into the 
