. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. 14 bulletin: museum of comparative zoology. coordinated with those of typical Coccosteans, allowance being made for the fact that the preorbital in the modern form appears to have reverted to its primitive cartilaginous condition. Similar instances of reversion, or degeneration of membrane-bones, occur among Chondros- teans and Teleosts. A tendency toward reversion would seem to be indicated also by the external occipital along its inner border, and the small plates surrounding the orbits show imperfect ossif
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. 14 bulletin: museum of comparative zoology. coordinated with those of typical Coccosteans, allowance being made for the fact that the preorbital in the modern form appears to have reverted to its primitive cartilaginous condition. Similar instances of reversion, or degeneration of membrane-bones, occur among Chondros- teans and Teleosts. A tendency toward reversion would seem to be indicated also by the external occipital along its inner border, and the small plates surrounding the orbits show imperfect ossification. The latter, according to the observations of Huxley, Traquair, and others, are sometimes incon- stant in number, the suborbitals tending to become fused into a single piece not unlike that of typical Cocco- steans (cf. Figs. C, D). The postorbitals of Neoceratodus are in- terpreted by Bridge1 as remnants of an obsolescent supraor-. Fig. C. — Left suborbital plate of Dinichthys terrelli Newb., from the Cleveland shale of Ohio. External as- pect, X £.. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Harvard University. Museum of Comparative Zoology. Cambridge, Mass. : The Museum
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Keywords: ., bookauthorha, bookcentury1800, bookdecade1860, booksubjectzoology
