390 TELEOSTEI 



The supratemporal does not cover the lateral fossa, and there is no sub- 

 opercular, but in most other respects the bones of the skull resemble those 

 of Hyodon. The upper branch of the post-temporal is incomplete or absent, 

 paired bones are attached to the basibranchials as in Mormyrus, and mid- 

 ventral adpleurals form a keel joining the pleural ribs below. As in 

 Hyodon, the ovaries are * free,' that is, not closed off from the abdominal 

 coelom. 



Notopterus, Lac. ; Africa and E. Indies ; Tertiary, Asia. Xenomystus, 

 Gthr. ; Africa, 



Family OSTEOGLOSSIDAE. The skull [55, 364] has a distinctly 

 primitive appearance, the superficial bones being close to the skin and 

 having a sculptured surface. The wide nasals, frontals, and parietala 

 meet in the middle line, and the supraoccipital scarcely reaches the 

 surface. As in most primitive Teleosts, there is an eye-muscle canal, 

 blind behind, an opisthotic, and, as a rule, a toothed parasphenoid, which, 

 moreover, sends out a process to articulate with the entopterygoid (p. 271). 

 Both the premazilla and maxilla are toothed, and share in forming the 

 margin of the mouth ; there is no supramaxilla. The interorbital septum 

 is but incompletely formed ; the orbitosphenoid when ossified is paired 

 (Arapaima, Ridewood). The dermal articular may be distinct from the 

 endosteal articular. The subopercular is small, often hidden behind 

 the preopercular, and likewise the interopercular. The scales are large, 

 thick, and cycloid. In Heterotis, at all events, the ovaries are free, and 

 the larva has external gills (Budgett [67]). The Osteoglossidae are 

 an ancient family dating from Eocene times ; they seem to be more 

 closely allied to the Albulidae than to any other family. In the more 

 specialised genera the caudal region is generally much developed, the 

 dorsal and anal fins may be extended, so that the pelvics are relatively 

 far forward. Heterotis has a spiral suprabranchial accessory breathing 

 organ (Hyrtl [233c]). 



Dapedoglossus, Cope ; Eocene, N. America. Brychaetus, A. S. W. ; 

 Eocene, England. Osteoglossum, Vand. ; Arapaima, Mull. S. America. 

 HeterotiSj Ehr. ; Africa. Scleropages ; Indo-Pacific. 



Family SAURODONTIDAE. An extinct family closely allied to the 

 Chirocentridae, but rather more primitive. An eye-muscle canal and a 

 normal symplectic are present. The parietals are separated. The riba 

 are sessile, the neural arches separate from the centra, and there are no 

 compound hypurals. Characteristic of the family is the setting of the 

 teeth in deep sockets. Sometimes a predentary bone is present (Sauro- 

 cephalus, Saurodon). 



Saurocephalus, Harlan ; Saurodon, Hays Cretaceous, Europe and 

 N. America. Cladocyclus, Ag. ; Cretaceous, Europe and S. America. 



Family CHIROCENTRIDAE. This family, present in Cretaceous strata, 

 but also surviving at the present day, is possibly derived from the 

 Saurodontidae, but differs from them in having the large teeth not in 

 regular sockets, the symplectic hidden by the quadrate and hyomandi- 

 bular. 



A normal postclavicle is not present. There is a large axillary 

 scale above the level of the pectoral fin. The large coracoids 



