258 HACHIRO YUASA 



branous, is connected with the proximal portion of each mandible. 

 The extensacuta (ec) is located near the ventral part of the ce- 

 phalic margin of the mandibularia. The mandibulariae, although 

 they vary in size and shape, are present and more or less well 

 differentiated in all except in Anisolabis (fig. 17). 



The occipital foramen (fig. 23, of) is the large subquadrate 

 opening located in the caudal part of the ventral aspect of the 

 head. It varies in size, shape, and position. The elongation 

 and the peculiar position of the foramen in Diapheromera (fig, 

 29) are due to the natural position of the head which is horizontal 

 instead of vertical as in the case of the other genera. 



In Blatta (fig. 23) the occipital suture (os) is distinct; it begins 

 at the lateral end of each postcoila and extends caudad, becom- 

 ing obsolete some distance from and slightly beyond the caudal 

 margin of the occipital foramen. The occipital sutures are pres- 

 ent in all except Diapheromera. They are practically complete 

 in Gryllus (fig. 28) and Tettix (fig. 35) where the caudal ends of 

 the sutures unite with the epicranial stem near its origin. In 

 other genera the caudal ends of the sutures are either free, as in 

 Melanoplus (fig. 30), Orchelimum (fig. 27), and Stenopelmatus 

 (fig. 31), or they merge into the furrows which extend on to the 

 vertex, as in Mantis (fig. 24) and Anisolabis (fig. 32). In Mantis 

 (fig. 41), Orchelimum (fig. 44), and Melanoplus (fig. 49) the 

 sutures are connected with the lateral margins of the occipital 

 foramen by an ental thickening or parademe (pm). The ceph- 

 alic portion of each occipital suture is produced as a parademe 

 in Gryllus an4 others. 



The occiput (oc) in Blatta (fig. 23) is the narrow crescentic 

 area surrounding the caudal one-third of the occipital foramen. 

 Since there is no suture (excepting the occipital suture on the 

 lateral boundaries) either on its caudal margin where it meets 

 the vertex or on its cephalic margin where it merges with the 

 postgenae, the exact boundaries of the occiput cannot be estab- 

 lished. The imaginary line drawn across the occipital foramen 

 just cephalad of the odontoidea (od) is here considered as the 

 cephalic limit of the occiput. In other genera the occiput varies 

 in size and shape and its caudal and cephalic boundaries are 



