( 



NO. 3 



I XSKCT ]T RAD SNULHiKASS 



best developed on the right. The molar area of the right mandible 

 consists of strong, heavy ridges forming a projecting surface ; the 

 ridges of the left jaw are low and their area does not project. The 

 two molar surfaces, therefore, fit one upon the other without interfer- 

 ence when the jaws are closed. The incisor lobes of the mandibles 

 close upon the ventral end of the hypopharynx, the molar surfaces 

 over its base, and the anterior contour of the hypopharynx is modeled 



AR 



Fig. 39. — Internal structure of the head of Dissosfcirn caroJ'uia, and the 

 mandible and its muscles. 



A, inner surface of right half of epicranium. B, tentorium and lower margin 

 of epicranium, ventral view. C, iimer view of right half of head, with right 

 mandible and its muscles in place. D, right mandible, postero-mesal view. 



a, posterior articulation of mandible ; SAp, abductor apodeme of mandible ; 

 gAp, adductor apodeme of mandible; AR, antennal ridge; AT, anterior tentorial 

 arm ; at, anterior tentorial pit ; c, anterior articulation of mandible ; Clp, clypeus ; 

 cv, cervical sclerite; DT, dorsal tentorial arm; E, compound eye; ER, epistomal 

 ridge ; es, epistomal suture ; Fr, f rons ; g, condyle of articulation of cervical 

 sclerite ; /;, subocular ridge ; /, subantennal ridge ; Lm, labrum ; Md, mandible ; 

 O, ocellus ; 0, incisor lobe of mandible ; p, molar area of mandible ; Poc, post- 

 occiput ; PoR, postoccipital ridge; PT, posterior tentorial arm; pt, posterior 

 tentorial pit; SgR, subgenal ridge; Smt, submentum ; Int, body of tentorium. 



according to the irregularities of the mandibular surfaces. The pos- 

 terior slope of the mandibular hinge lines cause the points of the 

 jaws to turn inward, upward, and posteriorly during adduction. At 

 the base of each molar area of the mandibles a flat brush of hairs (fig. 

 39 C, D) projects inward, and the two brushes come together anterior 

 to the mouth opening when the mandibles are closed, serving thus 

 evidently to prevent the escape of masticated food material from be- 

 tween the jaws. The anterior surfaces of the mandibles are overlapped 

 by the epipharyngeal surface of the clypeus and labrum, and the 



