OCR Text |
Show 1904.] OSTEOLOGY OP CLUPEOID FISHES. 465 two depressions, bounded externally by the epiotics. The epiotic has 011 its postero-superior surface a large, oval, smooth facet for articulation with the post-temporal; and from the apex of the epiotic there projects backward into the muscles of the trunk a separable osseous brush. A similar brush projects back from the apex of the supraoccipital, which has no crest or spine. The parasphenoid extends very nearly to the posterior end of the basioccipital, and although the right and left sides of the posterior outlet of the eye-muscle canal are formed by vertical laminae of the parasphenoid, there are no projecting posterior wings of this bone. The middle portion of the parasphenoid bears a sharp ventral keel. Neither parasphenoid nor vomer bears teeth. A small basisphenoid is present, but it has no descending portion bisecting the eye-muscle canal. The orbito-sphenoid is fairly large, and has a forwardly directed process that meets a backward growth of the combined prefrontal,s. A fontanelle is present in the roof of the skull between the mesethmoid and the frontals. Text-fig. 127. Cliatoessus erebi, right side of skull. For explanation of lettering see p. 493 Temporal and Preopercular Series (text-fig. 127).__The posttemporal is large, and the attachment of its upper limb to the postero-superior surface of the epiotic is cpiite intimate, and not by means of a broad loose ligament. The deep limb is rod-like and is attached to the back of the opisthotic. The third limb is P roc. Z ool. S oc.- 1904, Y o l . II. No. XXX. 30 |