504 



ZOOLOGY 



SECT. 



oc.cond 



region of the skull is drawn out into a long, narrow rostrum. Near 

 the anterior end of this is a rounded opening, the external nasal 

 opening, which is entirely bounded by the premaxillae the nasals 

 not extending so far forwards. An aperture in the nasal septum 

 corresponds to an actual perforation by which the nasal cavities 

 are in direct communication in the living animal. The pterygoids 



(pt.) are in the 

 form of flat 

 plates continuous 

 with the bony 

 palate ; they ex- 

 tend back so as 

 to form a part of 

 the walls of the 

 tympanic cavi- 

 ties. The tym- 

 panic (ty.) is an 

 imperfect ring 

 which does not 

 become united 

 with the periotic. 

 The mandible 

 consists of very 

 narrow styliform 

 rami, which are 

 not firmly united 

 at the symphysis. 

 The condyle 

 (cond.) is narrow, 

 rather more 

 elongated antero- 

 posteriorly than 

 transversely. 

 There are very 

 slight rudiments 

 of the angle and 



FIG. 1140. Echidna aculeata. Ventral view of skull and right ' . 



ramus of mandible, ang. angle of mandible ; and. oss. audi- prOCCSS (COT.). 



tory ossicles ; cond. condyle of mandible ; cor. coronoid process ; T jr pl fl f vrm 



max. maxilla; oc. cond. occipital condyle; pal. palatine; p. e JTlcH/ypllS 



max. pre-maxilla ; pi. pterygoid ; sq. squamosal ; ty. tympanic (][& 1139) the 



zygoma is stouter 



than in Echidna, and there is a post-orbital process which is formed 

 by the jugal. The maxillary root of the zygoma develops a process 

 which supports the horny tooth (dent.) of the upper jaw. The 

 nasal and premaxillary region is expanded into a rostrum which 

 is much broader than in Echidna. The premaxillse (pr. max.) 

 diverge from one another anteriorly, and then curve inwards again, 



