67 
broader behind than in front; it can be retracted into the cephalo- 
thorax just below the dorsal surface. This plate is divided by a median 
line or sulcus; on each side below and toward the tip there arises a 
long and slender curved stylet. This plate appears to be formed 
by the union and flattening of the basal joints of the mandibles. 
Fi<;.-2.— T(t, 
mandibular plate, dorsal and lateral views: a, plate 
l>;ilpus— highly magnified (original). 
b, stylet; 
Below this plate 4 is a rather large and conical rostrum, from each side of 
the base of which arises a palpus, each composed of five joints. The 
penultimate joint ends in a large claw; the last or "thumb" projects 
little if any beyond this claw, and bears one or more projections or 
"fingers™ on its tip or sides. In some species, perhaps all, tin 4 palpus 
of the male has a short, 
curved spine on the tip of 
the upper side of the third 
joint. The rostrum at tip 
has a cylindrical projec- 
tion, rather enlarged at 
the end. consisting of a 
piece each side, which i- 
possibly the maxilla. The 
opening between the two 
is the mouth. At the tip 
of the abdomen on the 
ventral surface Is the anal 
opening, often showing 
from above at the tip of a nice 
sliffhtlv in front of the ana 
Fig. 3.— T> tranychu* : eephalothorax from above: <\. paljNM; 
b, mandibular plate : r. frontal bristle : '/. subfrontal I>ri«.tle ; 
t, eyes — highly magnified (original). 
an pointed projection. < hi the venter 
orifice is the genital opening. In the 
female it is surrounded with variously curved 8tri»; iii the male it 
is much less conspicuous a simple slil inclosing a ratlin- -lender 
curved penis. The vulva in the various forms appears somewhat 
different, although on the same plan. Bui the difficulty of exam in- 
