LAMPRIDIFORMES 475 



Division 3. LAMPRIDIFORMES (Allotriogmathi). 



Quite recently the Taeniosomi of Gill have been joined with 

 the Lamprididae and the Veliferidae to form this Division by 

 Regan [348]. It is characterised by the compression of the body, 

 the peculiar mechanism of the protractile mouth, and the presence 

 of an orbitosphenoid (except in Sti/lephoms), a bone which has been 

 lost in all the Acanthopterygii except the Berycidae. 



The scales are reduced, being either very small or absent. The 

 covering bones of the skull are, for the most part, deeply sunk ; 

 there is usually a remarkably large occipital crest. Whilst in 

 other Acanthopterygii it is the premaxilla alone which slides 

 forwards on the ethmoid, when the maxilla is pushed forwards by 

 the palatine to protrude the mouth, in the Lampridiformes the 

 maxilla itself moves forwards, sliding on the vomer and ethmoid. 

 There is no supramaxilla, no subocular shelf, a short eye-muscle 

 canal, and no opisthotic. The paired fins are spineless, and the 

 pelvics may have as many as seventeen rays. The pelvic girdle is 

 more or less closely connected to the coracoids. The air-bladder 

 is closed, the dentition feeble. 



The Lampridiformes are all marine, of either pelagic or deep- 

 sea habit ; they are unknown as fossils. They appear to be 

 specialised forms derived from ancestors resembling the Berycidae, 

 and have now diverged in two directions. 



SUBDIVISION 1. 

 TRIBE SELENICHTHYES. 



Lampris (Fig. 401, C) has a very deep compressed body and spineless 

 fins ; the pelvics may have seventeen dermal rays. The pelvic bones 

 articulate with the very large expanded coracoids. Only three short 

 pectoral radials are present, one of which rests on the coracoid ; and the 

 dermal rays partly spring from the scapula. There are forty-six vertebrae, 

 without parapophyses, the ribs being strong and sessile. The maxillaries 

 take a share in the margin of the toothless mouth. 



Family LAMPRIDIDAE. Lampris, Retzius, the brilliantly coloured 

 King-Fish ; Mediterranean, Atlantic, and Pacific (Fig. 401, C). 



SUBDIVISION 2. 



The mesethmoid is behind the prefrontals, and the frontals 

 cover an anterior chamber on the skull. The two pelvic bones 

 project upwards between the coracoids. 



