| OCR Text |
Show 632 MR. W. G. RIPEWOOP ON THE [N 0V. 6, 2. O n the Hyoid Arch of Ceratodus. By W . G-. R I D E W O O D , B.Sc, F.L.S., Lecturer on Biology at St. Mary's Hospital Medical School. [Eeceived October 8, 1894.] Since the discovery by Huxley (5) of the hyomandibular cartilage of Ceratodus, but little has been published in the way of a detailed description of the hyoid arch, and as the intermediate position occupied by the Dipnoi between the Fishes and Amphibia renders a minute knowledge of every part of their anatomy of the greatest importance, the following short contribution may, by collating the views of various observers, be of some assistance to the student of ichthyopsidan anatomy. The most conspicuous element of the hyoid arch is the large ossified ceratohyal (figs. 1 and 2, ch), the extremities of which remain cartilaginous. Fig. 1. Ceratodus forsteri.-Hyoid arch, ventral view. (The hyomandibular is not shown.) ch, ceratohyal; hh, hypohyal; bh, basihyal. Towards its anterior end it is nearly circular in section, but proximally it becomes vertically compressed, with a delicately curved posterior edge ending abruptly against the terminal cartilage. The cartilage of the distal or anterior end articulates by a flat surface with the hypohyal. |
