316 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
the chelicerae or mandibles with their sheaths and digits (pi. 18, 
fig- 2, nid. sh., md. dig.) together with the hypostome or radula is 
forced into the hide of the host. When the beak has imbedded itself 
the mandibular digits are set at an angle with the mandibles by 
muscular action much as the points of a double-pointed harpoon are 
set in a load of hay. Thus the animal is firmly locked to its host so 
that the body of the tick is removed only by tearing loose from its 
capitulum or, as in this case, by removing a piece of the epidermis 
of the host. 
The bit of skin from the host has the appearance of the cone of 
a volcano as seen from above. The opening (pi. 18, fig. 2, or. haus .) 
is just the size of the anterior end of the beak. On either side of 
the elevation forming the cone is a shallow depression where the 
end of the corresponding palpus fits. 
The beak is like a rasp, with the mandibular teeth making its 
sharp point. The eight rows of backward-pointing teeth on the 
hypostome make the coarse side of the rasp, while the very small 
points on the dorsal side of the mandibular sheaths make the fine 
side. The hooked feet of the tick serve to hold the animal in place 
while it forces in this weapon. 
The palpi (pi. 18, fig. 2, pal.) lie one on each side of the mandibles. 
These are four-jointed and have many hairs over their surface. On 
the dorsal side of the capitulum near its base are found in the female 
tick two oval areas, the porose areas (pi. 18, fig. 2, por. ar.), which 
consist of a number of slight elevations each with a slit or pit at its 
apex. A pair of similar or smaller organs, the dorso-submedian 
porose plates, are found symmetrically placed on the back of the 
animal just behind the head shield. One of these is shown (pi. 18, 
fig. 3, d. sub-med. por. pi.), together with the marking on the surface 
of the surrounding cuticula. The round openings in the cuticula in 
this figure represent either the mouths of glands or the location of 
surface hairs or bristles (compare pi. 21, fig. 16. eta.). 
The whole surface is irregularly marked with very fine striae. 
Secondarily the cuticula is thrown into irregular undulations to con¬ 
form with organs within. It is depressed along certain definite lines 
where the internal musculature is attached. 
The cuticula in section (pi. 20, fig. 12; pi. 21, fig. 16, eta.) is from 
tV 1° v mm. thick. It is made up of two portions : an outer, more 
deeply pigmented layer, and an inner, pale layer. This inner layer 
