14 



SOME ASPECTS OF MORPHOLOGY 



on the cranial wall. Further back on the cranial wall lies the 

 post-occipital suture, which is very constant in its occurrence and 



,^Hpwy 



Fig. 6. The hypopharyngeal apophyses and the tentorium. A, 

 Under surface of head of Lithobius, mandibles and maxilla; 

 removed, showing suspensorial plates (HS) of hypopharynx 

 suspended from points (d) on margins of head, and hypo- 

 pharyngeal apophyses (HA) invaginated from their inner ends 

 and connected by ligamentous bridge (j) beneath pharynx. 



B, Head of Scolopeiidra, ventral, maxillae and right half of 

 cranium removed, showing attachment of mandibular adductors 

 (KL, KL) on ligament uniting the hypopharyngeal apodemes. 



C, Scutigera forceps, ventral view of hypopharynx {Hj)hy), 

 suspensorial plates {HS), their apodemes {HA) and uniting 

 ligament {j). D, Heterojapyx gallardi, ventral view of right 

 maxilla, hypopharynx {Hyph), and hypopharyngeal apodemes 

 {HA), upon which arise the muscles of the maxilla {cidmx), the 

 labium {Ibmcl), and the mandibles (not shown). E, Nesomachilis 

 maoricus, posterior view of unconnected anterior and posterior 

 arms of tentorium {HA, PT), part of the head wall with clypeus 

 {Clp) and labrum {Lm), base of maxilla {Mx), and mandible 

 (Md). F, Ephemerid nymph, ventral view of tentorium and 

 part of left side of head, showing anterior tentorial arms {AT) 

 arising from ventral margin of gena {Ge). (After Snodgrass.) 



appears to be of definite morphological significance. Internally 

 it forms the post-occipital ridge, which appears to be a true inter- 



