POLYPTERINI 



295 



is an elongated 'bone sharing but little in the support of the jaws. 

 There is no symplectic. Stylohyals, ceratohyals, and hypohyals are 

 present. There are only four branchial arches, all with cerato- and 

 hypobranchial, some with epibranchial, pharyngo- and supra- 

 pharyngo- branchial as well. The basibranchials are, however, 

 fused to a single plate. All the visceral arches are well ossified. 

 A pair of bones, analogous to and perhaps homologous with the 

 urohyal (p. 350), extend backwards from the ceratobranchials. 

 The chondrocranium is extensively preserved even in the adult. A 

 single ossification behind seems to represent the combined basi- 

 occipital and exoccipitals. In the auditory capsule are a large 

 opisthoti^, probably including the epiotic, and a small prootic closely 



d 



Fin. 267. 



Poltipterus bichir, Geoffr. Inner view of the lower jaw and hyoid arch, a, articular ; c, 

 ceratohyal ; d, dentary ; e, epihyal ; g, inferior gular ; h, hyomandibular ; o, small dermal 

 ossicle ; op, opercular ; p<\ preopercular ; so, subopercular ; sp, splenial. 



connected to the parasphenoid (van Wijhe [494])'. The cranial 

 walls between the orbits are strengthened by two peculiar bores 

 which surround the pituitary fossa and fuse ventrally ; these 

 1 sphenoids ' probably represent both the alisphenoid and the orbito- 

 sphenoid of other fish. 



The dermal pectoral girdle consists of paired clavicles, cleithra, 

 postclavicles, and supraclavicles (Fig. 212); the post-temporals are 

 closely connected with the skull (Figs. 2 65 A, 263). The endo- 

 skeletal girdle has an ossified scapula and coracoid, but no meso- 

 coracoid arch (p. 276). This, and the small size of the 'primary' 

 pectoral girdle, are points of resemblance with certain Teleosts. The 

 skeleton of the pectoral fin is very peculiar (Gegenbaur [153, 162], 

 Klaatsch [266]). It consists of two ossified basal rods, articulating 

 with the girdle, between which is a wide cartilaginous plate with a 

 bony centre. Attached to these is a row of distal ossified radials 



