276 Mr. A. S. Woodward on the Myriacanthide. 
Myriacanthus *, Tt is a fossil evidently having a wide range 
in Jurassic rocks, for, besides the English Liassic species, 
others are known from the Upper Jurassic of Bavaria t ; and 
it is thus remarkable that, until the present time, the precise 
relationships of the “ genus’ should have remained altogether 
undetermined. The British Museum now furnishes materials 
for the solution of the interesting problem; and it is the 
object of the present paper briefly to record the facts already 
available, with the zoological inferences that seem deducible 
therefrom. 
Myriacanthus is a long slender spine, somewhat laterally 
compressed, with a hollow internal cavity opening at the 
base. There is no indication of an inserted portion in the 
known specimens, the lateral ornament of small tubercles 
extending over the whole of the sides, except quite at the 
distal extremity; a sparse irregular series of large, thorn- 
shaped, spinous tubercles is arranged along each edge of the 
somewhat flattened, smooth posterior face, while a few similar 
tubercles also occasionally occupy the median line of this face ; 
and the anterior edge of the spine is provided with one such 
series of spinelets, at least in part of its extent. 
The first clue to the true nature of this Ichthyodorulite 
was received by the British Museum in 1870, when the fine 
Liassic fossil described by Egerton as [schyodus orthorhinus $ 
was added to the collection. In Egerton’s memoir, however, 
there is no allusion to the fact, which seems to have also 
escaped subsequent observers; and the only paleontologist 
who has recognized a striking novelty in the fossil is Prof. 
Dr. K. A. von Zittel§, who proposes to assign to it the 
generic name of Metopacanthus. 
The so-called “ /schyodus orthorhinus,” as made known by 
the type specimen, is remarkable in many respects. Although 
dating back to so remote a period as that of the Lias, it 
exhibits a singular prolongation of the snout precisely similar 
to that of the existing Callorhynchus. In the enormous size 
of the median frontal spine, however, it still remains unique. 
The last-named appendage is nearly similar in form to that 
of Squaloraja||; when not abraded its surface is covered 
* L. Agassiz, Rech. Poiss. Foss. vol. i. (1857), p. 37. 
+ Myriacanthus franconicus, G. vy. Minster, Beitr. Petrefakt. pt. iii. 
(1840), p. 127, pl. ili. fig. 8. 
¢ Sir P. Egerton, “ On a new Chimezroid Fish from the Lias of Lyme 
Regis,” Quart. Journ. Geol. Soe. yol. xxvii. (1871), pp. 275-278, pl. xiii. 
. a A. yon Zittel, ‘Handbuch der Palzontologie,’ vol. iii. (1887), 
i || W. Davies, “On the Rostral Prolongation of Sgualoraja poly- 
spondyla, Ag.,” Geol. Mag. vol. ix. (1872), pl. iv. figs. 1-3, 5. 
