Skeleton of a Chimeroid Fish (Ischyodus). 95 
Britain, however, such fossils have hitherto remained un- 
known, and Chimeroid fishes have been recorded solely on 
the evidence of detached teeth and spines. At last a single 
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 Museum, and is 
indebted to the kindness of Mr. T. J. George, F.G.S., 
Curator, and the Committee of the Museum, for the oppor- 
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 Zschyodus or to 
Ganodus; 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 Jschyodus. 
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 hooklets 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. Cl. k. bay. Akad. Wiss. vol. ix. (1862), p. 286, pl. i. fig. 1, 
and J. Riess, Paleontogr. vol. xxxiv. (1887), p. 6, pl. i. figs. 1-4, pl. ii. 
figs. 1-7.—Chimeropsis paradoxa, KK. A. yon Zittel, Handb. Paleeont. 
vol. iii. (1887), p. 114, fig. 126, and J. Riess, doc. et. p. 21, pl. ii. figs. 9- 
11, pl. iii. figs. 1-10. 
* Sir P. Egerton, “Qn some new Species of Fossil Fish from the 
Oxford Clay at Christian Malford,” Quart. Journ Geol. Soc. vol. i. (1845), 
pp: 229-282. 
