Skeleton of a Chinucroid Fish (Tschyodus). 95 



Britain, however, such fossils liavc hitliorto remained un- 

 known, and Chimairoid (islies have been recorded solely on 

 the evidence of detached teeth and spines. At last a sinG;le 

 specimen, comparable in many respects with the Bavarian 

 material, is forthcoming for discussion ; and this forms the 

 subject of the following notes. The writer observed the fossil 

 during a recent visit to the Northampton J\Iuseum, and is 

 indebted to the kindness of Mr. T. J. George, F.G.S., 

 Curator, and the Committee of the Museum, for the 0])por- 

 tunity of making a detailed study of the characters of the 

 specimen. 



The fossil is displayed on a small slab of hard clay from 

 the Oxfordian series of Christian Malford, near Chippenham, 

 "Wiltshire, and was evidently obtained from the same horizon 

 as that already well known to yield species of Lepidotus^ 

 Aspidorhynchus , and Leptolepis *. The skeleton is appa- 

 rently that of a laterally-compressed fish, being shown in 

 side-view ; and the cartilages seem to have been very slightly 

 calcified. The total length of the original fish probably did 

 not exceed 0*32 m., and its maximum depth would be about 

 0-045. 



The rostrum is unfortunately wanting and the cartilages of 

 the head are too much crushed and obscured for determina- 

 tion. Moreover the dentition is too imperfectly displayed to 

 decide whether the species is truly referable to Ischyodas or to 

 Ga7iodus; but as the latter genus has never been obtained 

 above the Lower Oolites, the specimen may be most probably 

 assigned to Ischyodus. The left palatine and vomerine 

 dental plates are shown from the external aspect, the latter of 

 the quadrate shape characterizing these plates in Ischyodus. 

 The greater part of the left mandibular plate is also exposed 

 from the outer face, showing the deeply sinuous oral border ; 

 and the corresponding element on the right side projects in 

 front, showing the very narrow symphysis. The individual 

 being a male, a large rostral spine occurs on the top of the 

 head, with a cluster of scattered dermal booklets below. The 

 base of this spine forms a triangular expansion, with a faint 

 median crest on the inferior attached face ; and the proximal 



math.-phys. CI. k. bay. Akad. Wiss. vol. ix. (1862), p. 286, pi. i. fif?. 1, 

 and J. Riess, Palseontogr. vol. xxxiv. (1887), p. 6, pi. i. figs. l-.'5, pi. ii. 

 figs. 1-7. — Chimceropsis paradoxa, K. A. von Zittel, Haudb. Palaeont. 

 vol. iii. (1887), p. 114, fig. 126, and J. Riess, he. cit. p. 21, pi. ii. figs. 9- 

 11, pi. iii. figs. 1-10. 



* Sir P. Egerton, " On some new Species of Fossil Fish from tlie 

 Oxford Clav at Christian Malford,'' Quart. Jouru Geol. Soc. vol. i. (1845), 

 pp. 229-232. 



