I02 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8l 



asymmetry of the mandibular surfaces and contours is reflected in 

 that of the epipharyngeal surface (fig. 42 A). 



The mandibles of Dissosfcira are moved, so far as the writer could 

 discover, only by tergal abductor and adductor muscles, which, as al- 

 ready explained, are the primitive tergal promotors and remotors 

 transformed in function by the change from a monocondylic to a 

 dicondylic articulation in the mandible (fig. 29 A, B, C). Small 

 ventral adductors of the mandibles arising on the hypopharynx and 

 on the tentorium persist in some of the Tettigoniidae ( figs. 20 D, 

 KLh, 2gC,KL}i, KLt), but these muscles appear to be lost in the 

 Acrididae, as they are in all higher pterygote insects. The fibers of the 

 functional abductors and adductors arise on the walls of the cranium 

 and are inserted on flat apodemal plates of the jaws. The abductor 

 apodeme is a small plate (fig. 39 D, 8Ap) arising from the articular 

 membrane close to the outer margin of the mandibular base and near 

 the posterior articulation (a). The adductor apodeme (pAp) con- 

 sists of two large thin plates borne upon a common stalk, which 

 arises from the articular membrane at the inner angle of the mandib- 

 ular base, and lies in the lateral angle between the anterior and pos- 

 terior arms of the tentorium (C). One plate extends dorsally in a 

 longitudinal plane, the other, which is smaller, lies in a transverse 

 plane. Each mandibular apodeme is a chitinous invagination from the 

 articular membrane close to the base of the jaw. The muscles of the 

 mandible correspond with the apodemes. They are as follows : 



8. — Abductor of the mandible. — A small fan of fibers, arising on 

 ventral part of postgena and on extreme posterior part of ventral half 

 of gena ; inserted on abductor apodeme of the mandible. 



p. — Adductors of the mandible (fig. 39 C). — Two sets of fibers 

 corresponding with the two divisions of the adductor apodeme. The 

 fibers of one set (pa) arise on dorsal wall of cranium, from a point 

 between compound eyes to occiput, with one bundle attached on post- 

 occiput (Poc) ; inserted on both sides and on posterior margin of the 

 median apodemal plate. Those of the other set (pb), inserted on the 

 transverse plate of the apodeme, arise on lateral walls of cranium 

 from subocular ridge (h) to postgena, and some of the posterior 

 fibers encroach upon outer end of posterior tentorial arm. 



THE MAXILLAE 



The maxilla of the grasshopper (fig. 40 A) is so similar to that of 

 the roach (fig. 25 A), already described, that its major features will 

 need no special description. It consists of a triangular cardo (fig. 

 40 A, Cd). a quadrate stipes (St), with a well-developed ])alpifer 



