478 TELEOSTEI 



The affinities of the Mastacembeliformes are obscure ; but they 

 appear to be highly specialised forms allied perhaps to the 

 Blenniidae, with which they are frequently associated. 



Fig. 507. 

 Mastacembehis argus, Gthr. (After Giuither.) 



Family Mastacembelidae. Mastacembelus, Gron. (Fig. 507), and 

 Rhynehobdella, Schn. — tropical Asia and Africa. 



Series 7. 

 Sub-Order 8. GADIFORMES (Anacanthini). 



Whilst showing many points of resemblance to some of the 

 Acanthopterygii (Blenniiformes), this sub-order preserves certain 

 apparently primitive characters which seem to indicate that it 

 branched oft' at an early time, and that the resemblances are due 

 more to convergence than to close affinity (Boulenger [42] ; 

 Regan [344a]). 



The cranial bones are mostly deeply sunk below the surface ; 

 the frontals are often fused ; the supraoccipital is well developed, 

 with a high median crest, and separates the parietals (Fig. 328) ; 

 the opisthotic is peculiarly large, growing downwards so as to 

 separate the prootic from the exoccipital. There is no eye-muscle 

 canal, and no basisphenoid. But by far the most important char- 

 acteristic of the Gadiform skull concerns the interorbital region. 

 Here the interorbital septum is membranous, and really only 

 developed below the cranial cavity ; for the narrow channel in 

 which run the olfactory nerves or tracts is a continuation of the 

 cranial cavity itself (Fig. 508). Indeed, in the Gadidae, alone 

 among the living Teleostei with the exception of the Cypriniformes, 

 the brain is continued far forwards, the olfactory bulbs being close 

 to the nasal sacs (Fig. 353). The olfactory nerves or tracts, then, 

 do not pass through the orbital cavities as in the higher Teleostei 

 (with the exception of the Galaxiidae). This peculiar relation of 

 the septum points to the origin of the Gadiformes from some remote 

 ancestral fish, possibly even outside the Group B in which they 

 are here provisionally included. Spinous rays are found only in the 

 dorsal fin of some Macrurids. The scapular foramen is between 

 the scapula and the coracoid, or rarely in the scapula (Gadomus). 

 The coracoid is imperforate. The number of pectoral radials varies 



