. The Bashford Dean memorial volume :. Fishes; Sharks; Fishes, Fossil. The Eynhryology of Heterodoyitus japonicus 701. and the cranium. In the skull of Hyhodus hasanus (my Text-figure 34), the cranium is rather short, with a relatively large orbit and with short postorbital and rostral regions. The jaws, which are relatively large and massive, are longer than the cranium, so that the hyomandibular suspensorium extends backward, while the upper jaw extends forward as far as the end of the snout. The rami of the mandible, though deep and massive behind, rapidly taper forward and meet in a com- p
. The Bashford Dean memorial volume :. Fishes; Sharks; Fishes, Fossil. The Eynhryology of Heterodoyitus japonicus 701. and the cranium. In the skull of Hyhodus hasanus (my Text-figure 34), the cranium is rather short, with a relatively large orbit and with short postorbital and rostral regions. The jaws, which are relatively large and massive, are longer than the cranium, so that the hyomandibular suspensorium extends backward, while the upper jaw extends forward as far as the end of the snout. The rami of the mandible, though deep and massive behind, rapidly taper forward and meet in a com- paratively feeble symphysis which does not extend so far forward as the front of the Text'figure 34. Restoration of the skull of Hyhodus hasanus Egerton, a little less than one-half natural size. The deeply shaded portion is the orbit. cr., cranium; hy., hyomandibular; I., one of the labial cartilages; m., lower jaw or mandible; q., quadrate region of the pal- atoquadrate. The lettering does not appear on the original. After Woodward, 1916, Fig. 3b. upper jaw. The palatoquadrate is weak and depressed at its anterior end, but deepens rapidly backward. According to Woodward, it can scarcely have articulated with the postorbital prominence of the cranium. According to Huxley (1876) the skull of Heterodontus is the link that connects the primitive amphistylic skull with the ordinary selachian skull, which is hyostylic. Like- wise, Goodrich (1909) wrote: ". . it is well established that Hyhodus and Synechodus had typical amphistylic skulls, with the palatoquadrate and hyomandibular as in the Notidani- dae and other primitive ; This view accords with Woodward's observa- tion (1886) that the skull of Hyhodus duhrisiensis is typically amphistylic, and with JaekePs interpretation of the skull of Hyhodus haujfianus (my Text-figure 28); but it does not harmonize with Woodward's later statement (1916) that the pterygoquadrate (palatoquadrate) of Hyhodus hasanus "
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