File:A treatise on zoology (1900) (14596820689).jpg

Identifier: treatiseonzoolo09lank (find matches)
Title: A treatise on zoology
Year: 1900 (1900s)
Authors: Lankester, E. Ray (Edwin Ray), Sir, 1847-1929 Bather, Francis Arthur, 1863-1934 Goodrich, Edwin S. (Edwin Stephen), 1868-1946
Subjects: Zoology
Publisher: London : A. & C. Black
Contributing Library: Robarts - University of Toronto
Digitizing Sponsor: University of Toronto

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Text Appearing Before Image:
erculum ; orb, orbit; pop,preoperculum; pa, parietal plates; pm-x, premaxilla; socc, siipraoccipital plate; st, supra-temporals; spl, splenial bearing tritoral teeth; sq. pterotic (squamosal); v, vomer bearingtritoral teeth ; x, small plate. usual bones have by a process of degeneration been split tip into anumber of small irregular plates, as in the Acipenseridae. Taking Mesturus as an example (A. S. Woodward (502)), we find AMIOIDEI 339 the snout covered with numerous plates; two large frontals partly-separated by a median bone ; irregular small bones representing theparietals, separated in the mid-line by a large occipital plate ; severalsmall supratemporals ; a single bone representing the pterotic and post-frontal ; the orbit limited below by small plates which extend over thesub- and preorbital region. There appears to have been a small oper-cular and a large preopercular extending over the cheek, an exceptionalthing amongst Actinopterygians ; no sub- or interoperculum. Only two
Text Appearing After Image:
Fig. 319. Mesod/yii macropterus, Ag. ; Upper Jurassic, Bavaria ; restored. (After A. S. Woodward,Vert. Palaeontology.) fr, frontal ; mcth, mesethmoid ; md, mandible, showing narrow dentary infront; op, opercular ; orb, orbit; pop, preopercular; pn, parietal; jimo;, jjremaxilla ; socc,supraoccipital; sq, pterotic (squamosal) ; v, vomer. The caudal region is destitute of scales. branchiostegal rays remain, and the place of the median gular is takenby a mosaic of small plates. The gill-opening is small. The jaws andpalate are much specialised to bear a grinding dentition. The maxillais slender and toothless. Sharj) prehensile teeth occur on the smallpremaxilla and dentary ; the slender toothless jDalato - quadrate archbecomes fixed for a considerable length to the basis cranii. On thesplenials and opposing fused vomers are longitudinal rows of bluntenlarged grinding teeth. As specialisation increases the rows becomefewer and more regular, and the teeth larger (Fig. 317). 340 AM 101 DEI T

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