96 SMITHSONIAN MTSCl'lLLANEOUS CULI.ECTIONS VOL. 8[ 



The facial aspect of the cranium is distinctly separated by the 

 epistomal suture (fig. 36A, B, r^-) from the clypeus, but there is no 

 demarked frontal sclerite. The apex of the f rons, however, is defined 

 in Dissostcira by two short remnants of the frontal sutures (B, fs) 

 diverging- from the end of the coronal suture (cs). The facial area 

 of the head is limited on each side by an impressed line (/{) extending 

 from the lower angle of the eye to the anterior articulation of the 

 mandible. The median part of this area forms a broad frontal cosfa, 

 margined laterally by a pair of sinuous carinae (/') reaching from the 

 top of the head to the lower part of the face. A short, transverse 

 suhantcnnal suture (j) lies on each side of the frontal costa just 

 below the level of the median ocellus. The inner ridges of these 

 subantennal sutures have a close relation to the attachments of the 

 more important muscles of the frons (fig. 38 D, ;'). The true frontal 

 area of the grasshopper, therefore, must include the region of these 

 sutures and extend dorsal to them between the bases of the antennae 

 into the angle between the short remnants of the frontal sutures. 



The lateral areas of the head (fig. 36 A) have no special character- 

 istics. The subgenal suture (sgs) on each side is continuous anteriorly 

 with the epistomal suture (es). The compound eye is surrounded by 

 a distinct suture forming a high ridge internally (fig. 39 A, OR), and 

 setting oft" a narrow rim, or ocular sclerite, around the base of the 

 eye (fig. 36, A, B, C). 



On the posterior surface of the head (fig. 36 C), the occipito- 

 postgenal area (Oc, Pge) is included between the well-marked occip- 

 ital suture {ocs) and the postoccipital suture {pos). In Dissosteira 

 the occiput and postgenae are continuous ; in Mclanoplus the occipital 

 arch is separated from the postgenae by a short groove on each side 

 on a level with the lower angles of the compound eyes. Posterior 

 to the postoccipital suture is the postoccipital rim of the head (Poc), 

 widened above and below on each side, to which the membrane of the 

 neck is attached. The postoccipital suture forms internally the ridge 

 on which the muscles of the neck and prothorax that move the head 

 are inserted (fig. 45 A, PoR). Laterally the postoccipital ridge is 

 elevated as a high plate (fig. 36 C,Fo/?), from the ventral ends of 

 which the posterior arms of the tentorium (PT) proceed inward. The 

 roots of the tentorial arms appear externally as long open slits in the 

 lower ends of the postoccipital suture (pt, pt). 



The clypeus and labrum form together a broad free flap (fig. 36 A, 

 B, Clp, Lni) hanging before the mandibles from the lower edge of the 

 frontal region. The fronto-clypeal, or epistomal, suture (es) is a 

 deep groove forming internally a strong epistomal ridge (fig. 39 A, 



k 

 Ml 



