HEAD, MOUTH-PARTS, ORTHOPTERA EUPLEXOPTERA 263 



fan-shaped portion is divided into a large, concave mesal part 

 and a small, triangular, cephalolateral part. A somewhat simi- 

 lar condition occurs in Gryllus, where the median carina is small 

 and affects the contour of the pretentorium only slightly. In 

 Diapheromera and Orchelimum a lateral furrow extends longi- 

 tudinally and tends to fold dorsad forming the lateroventral mar- 

 gin. In Stenopelmatus, Orchelimum, Melanoplus (fig. 39), Tet- 

 tix (fig. 40), and Anisolabis (fig. 42) the doi*somesal margin is 

 thickened and the lateral expansion concave. This concavity 

 reaches its maximum development in Anisolabis, where it forms 

 a cup-shaped pocket along the frontogenal suture and the 

 antennaria. 



The laminatentorium is usually well developed and its caudal 

 margin is often constricted and fused with the corpotentorium. 

 It is small in Diapheromera and almost wanting in Orchelimum 

 and Stenopelmatus. The line of fusion is distinctly indicated in 

 Mantis, Diapheromera, Gryllus, and Tettix. In Anisolabis the 

 line of fusion extends to the caudal margin of the corpotentorium. 

 There is a circular opening in the laminatentorium of Mantis, as 

 in Blatta, but the oesotendons are wanting. The laminaten- 

 torium is triangular and concave in Gryllus and Tettix and emar- 

 ginate on the dorsal aspect in Melanoplus. The plate-like pro- 

 jection on each mesal side of the pretentorium in Orchelimum 

 (fig. 43) and Stenopelmatus (fig. 44) may represent the vestige 

 of the laminatentorium. The dorsomesal thickenings of the 

 pretentoria are frequently continuous with the dorsolateral thick- 

 enings of the metatentoria, forming the X-shaped dorsal ridges 

 across the laminatentorium and corpotentorium. In Anisolabis, 

 however, this connection is obsolete and the caudal part of the 

 laminatentorium is elongated, an inverted trough-shaped struc- 

 ture, with a longitudinal depression on each side instead of a 

 dorsal thickening. 



The supratentoria arise from the cephalic part of the dorso- 

 lateral margins of the laminatentorium in all, except in Diaph- 

 eromera (fig. 51) where they issue from the pretentoria. They 

 are always small, linear, and expanded, adjacent to the 'amina- 

 tentorium; and in Gryllus (fig. 47) they are attached to the caudo- 



