Nos. IAND2.] ANATOMY OF SCOMBER SCOMBER. 83 



ficial layers and giving to it a superficial outline somewhat differ- 

 ent in every specimen. Roughly speaking it may be said to 

 usually have six edges or sides, and to be composed of the usual 

 two portions, a body and a mesial, horizontal process, or .wing. 



The body of the bone articulates posteriorly with the basioc- 

 cipital and occipitale laterale; dorso-posteriorly with the squa- 

 mosal ; dorso-anteriorly with the postorbital ossification ; and an- 

 teriorly with the alisphenoid. Antero-ventrally it is overlapped 

 by the lateral wing of the parasphenoid ; and ventrally by the body 

 of the parasphenoid. Dorso-posteriorly, where it adjoins the 

 sutural corner between the squamosal and occipitale laterale it is 

 overlapped, externally, and to a variable extent, by the intercalar, 

 this latter bone thus forming one of the bounding bones in external 

 views of the skull. The mesial, horizontal process "of the bone 

 articulates with its fellow of the opposite side of the head, and 

 with the alisphenoid and basisphenoid. 



Of these several so-called articulations those with the basioc- 

 cipital, occipitale laterale, squamosal, and postorbital ossification 

 are in greater part simply juxtapositions, the two articulating 

 bones being everywhere separated, excepting near the outer sur- 

 face, by a narrow, but distinct line of tissue or cartilage. At the 

 outer surface the thin, serrated plates that arise from the super- 

 ficial layer of the bone project, as thin splint-like processes, and 

 dovetail into corresponding processes or depressions on the edges 

 of the adjoining bones, thus giving rise to what seem to be the 

 beginnings of true sutural articulations. 



Where the petrosal adjoins the parasphenoid the edge of the 

 latter bone simply overlaps, superficially, the adjoining edge of 

 the petrosal. That part of the edge of the petrosal that is so 

 overlapped by the body of the parasphenoid, is edged with a broad 

 band of cartilage, which, at the hind end of the petrosal, turns up- 

 ward between that bone and the basioccipital, and is continued 

 as a narrow cartilaginous line separating the two bones. The 

 inferior edge of this band of cartilage is presented ventro-mesially, 

 and is separated from the corresponding edge of the band of the 

 opposite side of the head by the relatively wide hypophysial 

 fenestra. 



