. Chimæroid fishes and their development. Fishes; Chimaeridae. ins" of "Silurian Chimeeroid," Dictyorhabdus priscus Walcott. The first figure after Walcott. , oblique laminae in the structure of the fossil, suggesting lines of Fig. 115.—Dental plates of Men- aspis armala = Ctialcodus (permi- anus). Kupferschiefer. After spec- imen in Berlin Museum. DEVONIAN CHIM.^ROIDS. Chima>roid remains, or, more accur:itely, what are generally accepted as such, are widely distributed throughout the middle and especially the upper Devonian rocks of northern Europe and North America
. Chimæroid fishes and their development. Fishes; Chimaeridae. ins" of "Silurian Chimeeroid," Dictyorhabdus priscus Walcott. The first figure after Walcott. , oblique laminae in the structure of the fossil, suggesting lines of Fig. 115.—Dental plates of Men- aspis armala = Ctialcodus (permi- anus). Kupferschiefer. After spec- imen in Berlin Museum. DEVONIAN CHIM.^ROIDS. Chima>roid remains, or, more accur:itely, what are generally accepted as such, are widely distributed throughout the middle and especially the upper Devonian rocks of northern Europe and North America. These are referrtxl to the family Ptyctodontidae. Unfortunately for accurate diagnosis the are fragmentar}' and the best results which can be obtained from them are briefly these: That in the three genera—all at present known—Ptyctodus, Rhynchodus, and Palaeomylus, dental plates were present which resemble closely those of Chim?eroids. On the other hand, these plates were only four in number and their tritoral characters are puzzling. Within the substance of the plate appear not a few tubercular tritors, but a general series of tritoral points, sometimes arranged in lamella?, which in turn may form a series of flat or curving surfaces tritoral in function. The tritoral points are most conspicuous in Pt3'ctodus (fig. 116), where the}' form lamellae. In Pala?omylus (fig. 117) they spread out diffusely, and in Rhynchodus (fig. 118) are drawn together close to the rim of the plates, forming thus an extended sectorial *The nature of Dictyorhabdus was early commented upon by Hyatt, a reference which I had over- looked and for which I am recently indebted to my friend, Dr. C. R. 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 Dean, Bashford, 1867-1928. Washington, D. C. , Ca
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectfishes, bookyear1906
