CROSSOPTERl'GII. 



173 



24 25 



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

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

 accessory iiasal, 5 os terminale, 6 nasal, 7 anterior suborbital, 

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

 cular, 12 spiracular bones, 13 parietal, 14 post-spiraeular, ir, 

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

 culum ; 19 preoperculum, so quaclrate, 2/ jugals, 22. articular, 

 S3 angular, 34 dentary, S5 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- is 'f „^ I3i2 



illae, max- 

 illae and 



jugals (two). 



The hyo- 



m a n dibular 



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 



(i-) — the spiracular bones — in the flap which covers up the 



spiracle. 



There are also three supra-temporals i^-'^) and a post-temporal 



(i^) 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. 100. — Side view of palatoquadrate, hyomandibiUar and 

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

 2 palatine (small and not appearing in palate), .3 ectoptery- 

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

 operculum, S hyo'mandibular, 9 metapterygoid. 



