NO. 3 



INSECT HEAD SXODGRASS 



67 



of abduction in appendages with this type of articulation and mus- 

 culature. 



The Apus type of mandible is probably characteristic of most of 

 the more generalized Crustacea; it is present also in some of the 



PcR 



Md 



Fig. 27. — Mandibles of Crustacea and Apterygota. 



A, mandibles of Apjis longicaudata (phyllopod), anterior. B, mandibles of 

 Spirontocaris grocnlandicus (decapod), anterior. C, mandibles of Hetcrojapyx 

 gallardi (apterygote insect), anterior (dorsal). D, mandibles of Xcsoiiiachilis 

 maoricns (apterygote insect), posterior. 



a. articulation of mandible with cranium, or with wall of mandibular seg- 

 ment (IV); HA, hypopharyngeal apophysis; /, promoter of mandible; /, 

 remoter of mandible; k, median tendon of mandibular adductors of dumb-bell 

 muscle {KL or KLk) ; KLk, fibers of mandibular adductors united by tendon 

 {k) ; KLf, fibers of mandibular adductors retaining origin on hypopharyngeal 

 apophyses (D, HA); m, suspensory tendons of mandibular adductors; Md, 

 mandible ; PcR, posterior cranial ridge ; f, branch of labral muscle attached on 

 mandible. 



decapods (Virbiiis, Spirontocaris). In Spirontocaris (fig. 27 B), the 

 median ligament (k) of the dimib-bell adductors (KL) is connected 

 with the hypodermis of the dorsal wall of the body by a branched arm 

 (m) on each side. As before pointed out, however, the adductor liga- 



