HEAD, MOUTH-PARTS, ORTHOPTERA EUPLEXOPTER.\ 259 



more or less indefinite. In Melanoplus and others the obHque 

 parademes mentioned above form its cephalic margin. 



The postgenae (pgn) in Blatta (fig. 23) is the flat area cephalad 

 of the occiput and mesad of each occipital suture. The caudal 

 half of its mesal margin is bounded by the lateral margin of the 

 occipital foramen and the cephalic half is roundly emarginate and 

 continuous with the microcoria (ma). The postcoila (ptl) is lo- 

 cated on the cephalic margin. The relation of each postgena to 

 the adjacent areas is similar in all the genera studied, but it varies 

 in size and shape due largely to the difference in size and shape of 

 the occipital foramen. There is a distinct crassa (cr) adjacent to 

 and parallel with the cephalic part of the mesal margin of each 

 postgena which extends from near the middle of the postcoila in 

 Gryllus (fig. 28) and from the lateral end in Anisolabis (fig. 32). 

 On the ental surface of the crassa, there is a corresponding para- 

 deme. This parademe is present in all and extends from each 

 postcoila to the occipital foramen along the mesal margin of 

 each postgena. 



The postcoila (fig. 23, ptl) is the blackish acetabulum in which 

 the postartis of the mandible articulates. It is located at the 

 cephalic margin of each postgena. It is usually distinct and well 

 developed, being largest in Gryllus, comparatively shallow in 

 Diapheromera, and located on the mesal angle of tlie cephalic 

 margin of the postgena in Melanoplus and Tettix. 



The metatentorina (mn) in Blatta (figs. 13 and 23) is the elon- 

 gated opening located on each side of the cephalic margin of the 

 occipital foramen between the maxillaria and the postgena and 

 leading into the corpotentorium. It is always present and dis- 

 tinct and similar in position, but varies in size and shape. 



The paracoila (pi) in Blatta is the condyle-like projection 

 formed by the cephalolateral angle of the maxillaria protruding 

 ventrocephalad on each side of the occipital foramen. It is 

 folded longitudinally upon itself, the crest of the fold forming a 

 condyle and the concavity an acetabulum. The margin, near 

 the lateral portion of each paracoila, is emarginate and forms the 

 other side of the acetabulum. The exparartis of the maxilla is 

 articulated against this condyle and acetabulum. The para- 



