| OCR Text |
Show 1886.] ON THE COLUMELLA OF ICHTHYOSAURUS. 405 10. Note on the Presence of a Columella (Epipterygoid) the Skull of Ichthyosaurus. By A. SMITH W O O D W A R D, F.G.S., of the British Museum (Natural History). (Communicated, by Professor FLOWER, LL.D., F.R.S., President.) [Received June 3, 1886.] In the skulls of fossil Reptiles and Amphibia it so rarely happens that the bones on the inner side of the temporal fossa, and those between the orbits, are well exposed to view, that even in some of the most familiar genera very little has yet been ascertained regarding the special characters of any of these ossifications. In so conspicuous a form as Ichthyosaurus, for example, there appears to be no published reference to these structures beyond the brief statements of Profs. Huxley, Cope, and Sir Richard Owen, and even these do not afford any very definite information. Prof. Huxley determinedx the presence of a distinct pro-otic, and the doubtful absence of ali- and orbito-sphenoids ; Prof. Cope gives2 a diagrammatic outline of the "columella"; while Sir Richard Owen appears to have been less successful in his researches, having met with nothing but unsatisfactory indications of small " alisphenoids " (? pro-otics), and especially remarking that there is " no trace or sign of the Lacertian columellar bone" 3. In making the latter statement, the distinguished palaeontologist just mentioned evidently overlooked Prof. Cope's previous researches upon the osteology of the Ichthyosaurian skull; and having lately discovered that there is no foundation for the assertion in the British Museum specimens, that formed the basis of Sir Richard Owen's monograph, I venture to offer a few remarks upon the subject, by way of pointing out the mistake. A detailed description of the interesting bone in question may also be acceptable, since Prof. Cope's materials appear to have been less complete and satisfactory than those now afforded by the fossils from the English Jurassic. The first specimen of interest in this connection is a small slab of Lias from L y m e Regis, exhibiting a number of dislocated cranial bones, which Mr. William Davies long ago recognized as belonging to Ichthyosaurus, but which do not appear, hitherto, to have been submitted to so careful a study as their admirable state of preservation renders desirable. In the middle of the fossil, the basioccipital, basisphenoid, and presphenoid are arranged in irregular series, with their upper aspect exposed ; in front are the remains of the supra-occipital and parietals ; and on either side are scattered a number of 1 T. H. Huxley, 'Anatomy of Vertebrated Animals,' 1871, p. 211. 2 E. D. Cope, " On the Cranium of the Iehthyopterygia," Proc. Amer. Assoc. Adv Sci. vol. xi'x. (1870), pp 200-203. (For this reference I am indebted to the kindness of Mr. J. W . Hulke, F.R.S.) 3 R. Owen, " Fossil Reptilia of the Liassic Formations.-III." (Mon. Pal. Soc. 1881), p' 96; also, 'History of British Fossil Reptiles,' vol. iii. (1884), p. 54. |
