THE COCKROACH. 347 



epicraniiim, and is firmly united with it only on its dorsal side. 

 This band forms the boundary of the so-called occipital fora- 

 men^ by which the cavity of the head communicates with that 

 of the neck, the chitinous wall of the latter region being con- 

 tinuous with it. Articulated at right angles with the cardo 

 is the stipes, or second joint of the maxilla. This is freely 

 movable in the lateral direction, and its outer distal angle 

 bears the continuation of the limb, or palpus, formed by two 

 short and three long joints. Two processes terminate the 

 stipes ; of these, the anterior and outer — the galea — is soft, 

 rounded, and possibly sensory in function, Avhile the posterior 

 and inner — the laci)iia — is a curved cutting blade with a 

 toothed and spinose inner edge. 



The labium (Fig. 97, III.) consists of two incompleteh^- 

 separated median plates, the si(bmentiim behind, and the oneii- 

 tum in front ; upon the latter follows a bilobecl terminal piece, 

 the ligula, each lobe of which is again divided longitudinally 

 into two portions, which have considerable similarity to the 

 galea and lacinia of the maxilla. The outer is usually termed 

 W^Q p)aTaglossa. 



Betw^een the mentum and the ligula, on each outer edge 

 of the labium, a small piece, the palpAger, is articulated ; it 

 bears the three-jointed labial palpus, which is to be regarded 

 as the proper free termination of the second maxilla. The 

 resemblance between the labium and a pair of maxilla? which 

 have coalesced, is obvious. 



The submentum is not directly articulated with the cranial 

 skeleton, but its posterior edge is close to one of the cervical 

 sclerites^ or skeletal elements observable in the chitinous in- 

 tegument of the neck, of which there are altogether seven. 

 One is dorsal, median, and marked by a deep longitudinal 

 depression. It articulates with the dorsal margin of the oc- 

 cipital foramen. Four are lateral, two Qn each side (Fig. 97, 

 L, Ic) ; these take an oblique course from the dorsal part of 

 the boundary of the occipital foramen, with a tubercle of 

 which the anterior piece is articulated, to the anterior edge 

 of the episternum of the prothorax. The inferior cervical 

 sclerites (Fig. 97, I., ic) are two narrow transverse plates, one 

 behind the other in the middle line. They appear to repre- 

 sent the part called gula, which, in many insects, is a large 



1 I use tliis term in tlie sense in wliicli it has been employed by Milne- 

 Edwards, to denote any definite hardened part of the chitinous skeleton. It 

 is to the latter what a distinct ossification is to the skeleton of a vertebrated 

 animal. 



