. The Bashford Dean memorial volume :. Fishes; Sharks; Fishes, Fossil. |#t| Text-figure 13. Placoid scales from two species of the Devonian shark Cladoselache. A—Scales (x 25) from various parts of the body of C. fyleri. From a specimen in the American Museum. B—Trifid scale (x 20) from near margin of mouth of C fyleri. From a specimen in the American Museum. C—Larger scales (x 10) of Cladoselache (probably clarl^). From a specimen in the British Museum. After Dean, 1909, Figs. 1, 2, 3. In Chlamydoselachus and in Heptanchus (Daniel, 1934, Fig. 27) the structure of the scales is simple and conf
. The Bashford Dean memorial volume :. Fishes; Sharks; Fishes, Fossil. |#t| Text-figure 13. Placoid scales from two species of the Devonian shark Cladoselache. A—Scales (x 25) from various parts of the body of C. fyleri. From a specimen in the American Museum. B—Trifid scale (x 20) from near margin of mouth of C fyleri. From a specimen in the American Museum. C—Larger scales (x 10) of Cladoselache (probably clarl^). From a specimen in the British Museum. After Dean, 1909, Figs. 1, 2, 3. In Chlamydoselachus and in Heptanchus (Daniel, 1934, Fig. 27) the structure of the scales is simple and conforms to the same fundamental plan, though in both fishes the form of the scales varies considerably on different parts of the body. One should not attribute much phylogenetic importance to differences in the form of the scales of elas' mobranchs. Some of the most specialized elasmobranchs (, Raja) have simple scales, while the fossil Cladoselache, one of the most primitive sharks, has scales of various forms ranging from those only slightly indented or subdivided (Text'figures 13a and b) to those indented to such a degree that their exposed surfaces bristle with cusp'like points or ridges (Text-figure 13c.) In Cladoselache as in modern sharks, the scales vary in size and shape in different regions of the body (Dean, 1909, p. 214). The teeth of Chlamydoselachus are barb-like, prehensile. In Heptanchus (Text-figure 14) the teeth are not alike on upper and lower jaws. The upper teeth seem adapted mainly for holding, the lower ones for cutting. The decided differences between the teeth of Chlamydoselachus and Heptanchus—forms which, in many important respects, seem closely related— serve to weaken one's faith in the validity Text-figure 14. Dentition of Heptanchus (AJotidanus) indicus. a, teeth in function; fa, teeth in reserve; u and I, upper and lower single teeth (natural size). From Goodrich, 1909, after Giinther,. Please note that these images are extracted from
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