456 CALIFORNIA ACADEMY OF SCIENCES. 



of the head. The facet presents the peculiarity of having 

 no inner wall, and is separated only by a constriction 

 from a large cavity in the anterior thickened part of the 

 mandible. This cavity is elongated in a line extending 

 from the facet to the two teeth of the mandible. The 

 posterior wall of the cavity is very thin. 



Attached to the dorsal border of the inner angle of the 

 mandible is a large thin chitinous plate (plate lxi, fig. 9, 

 ch. pis.). This plate is thickened proximally and appears 

 here darker than the rest. This part is also narrow, but 

 distally the plate expands and becomes very thin and 

 transparent. The distal border is not definite, being very 

 thin and generally irregularly broken away. Attached 

 to this plate are the retractor muscles of the mandible. 

 The plate and muscles extend dorsally and very slightly 

 backward from the mandible, since they lie in the same 

 plane as the latter. From the outer posterior angle of 

 the mandible there extends dorsally and outward a slender, 

 very thin, chitinous structure, which bears the extensor 

 muscles of the mandible. These two sets of muscles are 

 attached to the dorsal wall of the head. The left mandi- 

 ble is very similar to the right. The two teeth are more 

 separated and are sharper. The process projecting 

 inwardly from the base is slenderer and longer than on 

 the right mandible. It arises a little ventral to the dorsal 

 inner angle, and is slightly rounded ventrally, while the tip 

 is again turned a little in the same direction. The 

 muscles are attached in the same way as in the case of 

 the right mandible. To the dorsal inner border, of 

 each mandible there is attached, also, internal to the 

 attachment of the plate, a fringe of large muscle fibers; 

 these appear to be a second set of retractor muscles. 



In Goniodes cervinicomis there is a pharyngeal sclerite 

 and pair of glands which are in every way similar to those 



