POLYPTERINI 



293 



and the anterior nostril has a tubular prolongation, 

 cranial bones depart consider- 

 ably from the typical Teleostome 

 arrangement (Figs. 265A, 266). 

 On the one hand, some bones 

 seem to have fused together; on 

 the other, a large number of small 

 additional plates are present (Allis 

 [13, 14], Collinge [87], etc.). The 

 pterotics (squamosals) and parietals 

 are represented by a single pair 

 of bones in which run the lateral- 

 line canals. Behind these parietals 

 is a transverse row of paired supra- 

 temporals. The .post -frontal is 

 hidden below the frontal, and the 

 post-orbital is the first of a long 

 series of small ossicles extending 

 back to the operculum. Some of 

 these are movable and cover the 

 external opening of the persistent 

 spiracle, situated at the outer side 

 of the parietal (Fig. 266, A). The 

 cheek is protected by a large pre- 

 opercular plate, harbouring the 

 hyomandibular sensory canal. An 

 opercular and a subopercular are 

 present in Polypterus, but no inter- 

 opercular ; in Calamoichthys neither 

 subopercular nor interopercular 

 are found. There is a pair of 

 large ventral gular plates only ; 

 the lateral gulars have been lost 

 (Fig. 273). In the lower jaw are 

 found an articular, a dentary, and 

 an angular (dermarticular ?) ex- 

 ternally, and a toothed splenial 

 internally. The latter has a strong 

 coronoid process, near which lies 

 a labial cartilage. The ^palate has 

 a large parasphenoid, spatulate in 

 front, paired vomers, ectoptery- 

 goids, and endopterygoids, all 

 covered with small teeth. A small 

 endochondral palatine hidden be- 

 hind these articulates with the prefrontal. 



The dermal 



A metapterygoid is 



