PLATE I— concluded. 



Fig. 8. — Head of Decticinas. 



E. SU. — Epicranial suture as in Orchelimutn. 



F. — Front containing trace of median ocellus. 



C. — Clypeus. All divisions of clypeus indicated. Suture between 

 front and clypeus present. 



At. — Tentorium invaginations present. 



L. — Labrum present. 



Tr. — Trochantin of mandible present. 



Fig. 9. — Head of Grasshopper. 



E. SU. — Epicranial suture pushed up to point of vertex (v). 



F. — Front large; bears ocelli. 



C. — Clypeus. Suture between front and clypeus present. Divided by 

 transverse suture into first and second clypeus. 



Ac. — Anteco.val pieces indicated. 



At. — Tentorium invaginations present. 



L. — Labrum appears to be divided into two parts by transverse suture. 



Tr. — Trochantin of mandible small but present as a distinct sclerite. 

 Fig. 10. — Head and Neck of Cockroach. 



This drawing shows the lateral view of the epicranium, which includes 

 all of the paired sclerites of the skull and sometimes also the front. The 

 paired sclerites constitute the sides of the head and that portion of the 

 dorsal surface that is behind the arms of the E. SU. These sclerites are 

 so closely united that Straus-Durckheim considered them a single piece. 



V. — Verte.v, the portion of the epicranium which is next the front and 

 between the compound eyes. In some insects it bears the paired ocelli, 

 but not in the Plecoptera. 



G. — Gense, lateral portions of the epicranium. 



Pg. — Postgense. The gense are divided by a well-marked suture, which 

 in the specimens at hand ended definitely. The part back of this suture 

 is known as the postgena. When this suture continues to the epicranial 

 suture the upper parts form the occiput. 



Tr. — Trochantin of the mandible. 



Md. — Mandible. 



Mx. — Maxilla. 



Mem. — Maxillary epimeron. A very small, narrow sclerite just back 

 of the postgense. 



This drawing also shows one dorsal, two lateral, and one ventral cer- 

 vical sclerite. 



Fig. 11. — Head of Adult Corydalis, Ventral Aspect. 



This drawing shows a gula, a sclerite forming the ventral wall of the 

 hind part of the head in certain orders of insects and bearing the labium 

 or second maxillae. 



In the more generalized orders this sclerite or the one corresponding 

 to it does not form a part of the skull. 



