COMTAKATIVE STIHV Ol" SCOMWIOIH I'ISHES. ;}19 



the supnioccipifabl iiud ptcmtios. VmAi cxoccipibil divor^os Huterüjrly, and 

 extends jUso kter:dly iu the Plecostei. . In the Sconibridio and Gramm dorcynm 

 there is au impiXBsion of the clavicuLir ligament on the bi>ne. In tlie Cj-biidio 

 and riecostei the bone bom's, on the doi'sal side, an anxihary interiiiiLScular 

 lK)ne near the foramen magnnm, ;ind sometimes ano'.her auxiliiu'v one in a 

 httle anterior and superior position. On the veutiid side there is a large 

 foramen for the exit of the vagus. In the Katsn .\ ouidio the cxt)ccipit!vls are 

 fusetl at the dorsal ii avgin to form a prominent doi-sal median crest, wliich 

 lies just l)elow the supraoccipiüil crest. The exoccipibd ci'est is l)e^t devclüix;d 

 in Auxis. On tlu^ inner side of the exoccipital, thciv; are two or tlu-ee grooves 

 anterior to the origin of tlie spinal cord to receive a part of the auditory 

 organ. 



Tl)e opisthotics are alwa^-s found in the so-called scombroid fishes, and 

 are genemlly seen from the dorsal as well as the venti'al side of the 

 skull ; but iu the Scombridje they do not appear at the doi-sa,] side of the 

 skull, except the articulating knob for the posttemporal. These bones lie on 

 the exterior side of the exoccipitals, and ar(> Ixiuuded by the prootics and 

 pterotics on the anterior and exterior sides. They forma part of the ix)steriür 

 wall of the brain-case. They have a large rough pi'ocess for the iirticulation 

 of the hollow end of the lower process of the iMsttemporal on the dorsid side. 



The basioccipital is a lx)ne with a concave occipital condyle Uihind, and 

 a very deep concavity on the opposite side, lying just below the floor of the 

 foramen magnum. The lx)ue is lx)nnded alxive by the exoccipitids, in fi-ont 

 by the prootics, and ventrally by the parfispheuoid. In the Scombrid« and 

 CybiidsQ it is a ruvrrow bone with nearly' parallel horizontal sides in the lateral 

 view. In the Plecostei the bone is produced ventiully Ixilow the horizon of 

 the vertebral column. This is easily understood if you compare the sideview 

 of skeletons of diiTerent families in the accompanying plates. The expanded 

 hitend wings of the basispheuoid overlap the posterior end of the parasphenoid 

 from outside, protecting the pxrasphenoi(Lü cliambcr. 



Tlie nasals are more or less elf)ngated flat bones, fii-mly joined to the 

 anterior margin of the frontals, anil the anterit)r end of these bones rests ou 

 the palatines. 



The preorbitals are also flat, elongated bones with an articulating surface 



