CROSSOPTERi^GII. 



173 



Fig. 99. — Side view of skull of Polyptenis with membrane bones 

 (after Traquair). 1 Nasal opening, a nremaxilla, 3 ethmoid, 4 

 accessory nasal, 5 os terminale. t> nasal, 7 anterior suborbital, 

 S posterior suborbital, 9 postirontal, 10 frontal, 11 prespira- 

 cular, la spiracular bones, 13 parietal, 14 post-spiracular, ir> 

 supratemporal, 16 post-temporal, 17 operculum, 18 sub-oper- 

 culum ; 19 preoperculum, an quadrate, 2i jugals, 22, articular, 

 2.'! angular, 24 dentary, 2.5 maxilla. 



entopterygoid, metapterygoid and quadrate ; the lower jaw has 



an articular and mento-meckelian cartilage bone and an angular, 



splenial and dentary, the two latter being dentigerous. On the 



upper jaw 



are premax- 



illae, max- 

 illae and 



jugals (two). 



The hyo- 



m andibular 



is ossified 



and bent ; 



there is no 



sy mplectic. 



There is an 



ope rculum, 



s u b o p e r- 



culum and 



a large bone 



called preoperculum. There are also circumorbital bones and 



pre- and post-spiracular bones (Fig. 99), as well as two bones 



{12) — the spiracular bones — in the flap which covers up the 



spiracle. 



There are also three supra- temporals (13) and a post-temporal 



{16) on each side. The membrane bones are in the skin and their 



outer surfaces are smooth and tuberculated, and not exposed in 



uninjured speci- 

 mens. The pre- 

 maxillae and 

 maxillae bear 

 teeth, and the 

 vomers, ptery- 

 goid and para- 

 sphenoid are 

 covered with 

 fine closely set 

 teeth. 

 The cartilaginous shoulder girdle is small and contains a scapular 



and coracoid ossification ; it is overlaid by a series of clavicular 



bones, of which the supraclavicle is attached to the post- temporal; 



Fig 



[~;;j-^;^.7^.»>.^;^-^ 



palatognadrate, hyomandibular and 

 opercular bones of Polyptenis (after Traquair). 1 vomer, 

 2 palatine (smr.ll and not appearing in palate), 3 e'^toptery- 

 eoid, 4 entopterygoid, 5 quadrate, 6 subopcrculum, 7 

 operculum, 8 hyomandibular, 9 metapteiygoid. 



