286 scr^NiD^. 



than the anterior; consequently the posterior angle is much more 

 acute than the opposite. There are five other cavities besides, on 

 each lateral half of the upper surface of the skull, three of which 

 are complete by bony ridges. These are situated as follows : — 



1. A pentagonal cavity between the central cavity and the upper 

 margin of the orbit. 



2. A pentagonal cavity on the temple, between the former and the 

 posterior infraorbital bone. 



3. A triangular cavity between the anterior part of the central 

 cavity and the upper anterior angle of the orbit, with its smallest 

 side in front, and an acute angle posteriorly. 



4. There is, in front of the latter, another incomplete cavity, the 

 bottom of which is formed by the turbinal bone. 



5. The other incomplete ca\ity is situated on the side of the occi- 

 pital crest, behind the cavity no. 1. 



All these cavities are in open communication with one another, the 

 bars extending from one point to the other like arches of a bridge. 



The lower part of the skull is very much swollen, globular ; this 

 is not an enlargement of the capsule of the brain, but it contains the 

 large otolithes which are observed in the fishes of this family. 



The infraorbital arch is formed by six bones ; they are all broad, 

 very thin, with a stronger orbital ridge, from which radiate other 

 transverse bars, dividing the infi-aorbital channel into as many 

 cavities. This channel communicates anteriorly with the foremost 

 cavity of the upper surface of the skull (4), posteriorly with the 

 pentagonal cavity described (2). The first and second infraorbital 

 bones form one straight continuous margin, rectangular to that of 

 the third. The thii-d has two transverse bars, the fourth, fifth and 

 sixth severally one, and the ridge of the sixth foi-ms one side of the 

 pentagonal ca\ity (2). The Hmbs of the prceoperculum are likewise 

 transformed into a muciferous channel by the elevated interior ridge. 

 This channel passes below into that of the mandibula, and above 

 into the pentagonal cavity, and is itself divided into five grooves. 

 The margin of the praeoperculum is very thin, and there are visible 

 about five very fine spines at its angle, which is rounded. The oper- 

 culum is triangular, the upper side slightly convex, the lower con- 

 cave ; near its upper side and on the interior surface it has a bifur- 

 cating crest, each part of the fork terminating in a flat obtuse point ; 

 the lower point is the longer, and separated from the upper by a small 

 notch. The inter- and suhoperculum are elongate, eUiptical. 



The glossohyal is triangular, rather short, broadest anteriorly ; the 

 epi-, cerato- and hasi-hyal bones are imited to one bone, bearing the 

 branchiostegals, which, seven in number, are all narrow, sword- 

 shaped, the first thin, rib-like. The urohyal is a thin plate, 

 strengthened by two longitudinal ridges on each side. 



The bones of the humeral arch are thin and flexible ; there are, on 

 the suprascapula, some very dehcate ridges, foi-ming a quadrangular 

 groove, by which the muciferous channels of the skull are continued 

 into that of the lateral line. The other bones of the humeral arch 

 are formed as usually, except the davicula, which has a prominent 



