290 BRITISH TYKOGLYPHIM;. 



longitudinal sulcations, which vary in number and 

 form, and are not constant in the individual ; they 

 are probably due to muscular strain ; they are most 

 conspicuous in lately emerged specimens, and are 

 usually lost in dead creatures and preparations. 

 Anterior legs short and thick ; the first pair (PL XIX, 

 fig. 15) pass the point of the rostrum by about the 

 length of their two distal joints ; there are a few fine 

 hairs, principally on the tarsus. In the first three 

 pairs of legs the claw is rather long, but only very 

 slightly curved. The fourth leg (PI. XIX, fig. 16) has 

 the coxa and femur very thick, but diminishes rapidly 

 toward its distal end ; the tarsus terminates in a 

 straight, fixed spine, probably the homologue of the 

 claw ; and two hairs, one of which is at least twice as 

 long as the leg, the other shorter but still long. There 

 are three or four other hairs, or spines, on the tarsus. 

 The ventral surface is flat with a concave median 

 channel at the posterior end to hold the hairs of the 

 host. Mouth-opening, which is a small round hole, 

 covered by a broad, thin, flat, pyriform, transparent 

 lip (PL XVIII, fig. 9). Epimera of first pair of legs 

 joined to the sternum ; the others free. There are 

 epimera both anterior and posterior to the second legs ; 

 those of the third pair of legs almost surround the 

 coxae, and have two spurs directed backward ; there 

 are not any to the fourth pair. The anus is a longi- 

 tudinal slit placed between the fourth coxae ; its labia 

 can be widely opened, and they generally assume this 

 position after death, and indeed retain it for long 

 periods during life. There are two pairs of minute 

 hairs behind it. The holding (homopial) plates (PL 

 XIX, fig. 17) are a pair of broad, thin, chitinous, 

 somewhat flexible, wing-like expansions, whose form 

 can be best understood from the figure ; they are 

 attached by the edge nearest the lateral side of the 

 body and fold inward, most frequently crossing a little ; 

 they are semi-transparent ; on the upper surface, i. e. 

 that next the body, are a number of fine, curved, 



