624 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 22, 
very singular fish that have been obtained from the Marl-slate of 
this country. 
The Midderidge quarry, in which these examples were found, is 
situated on the Darlington and Wear Valley Railway, not far from 
Bishop’s Auckland, and is well known as being the locality where 
the Marl-slate fishes were first discovered. Prof. Sedgwick a long 
time ago (Trans. Geol. Soc. 2nd series, vol. iii. pp. 76, 77) accu- 
rately described the position of this quarry and the Sep in 
which these specimens were found. 
Through the kindness of Mr. Duff, we have had the opportunity 
and pleasure of examining and studying all the specimens of this 
interesting fish: and this has happened fortunately ; for each spe- 
cimen, being in a different state of preservation, has assisted much 
towards the working out and comprehension of the structure of this 
extraordinary ichthyolite. 
When Mr. Duff’s original specimens were first seen, they were 
supposed to be merely the skeletons of a species of Platysomus ; but 
a short examination soon showed that this opinicn was entirely 
erroneous ; and happily the discovery of two more specimens, and 
especially of one in which the characteristic dorsal fin was better 
preserved than in the former specimens, led us at once to identity 
Mr. Duffs discovery with the Dorypterus Hoffmanni described 
originally by Prof. Germar in Count Minster’s Beitrage zur Petre- 
factenkunde (Heft v. pp. 35-37, tab. xiv. f. 4), from a specimen 
obtained from the Kupferschiefer of the Eisleben district. . 
Also there appears to us not the least doubt that the two fishes 
described by Count Miinster in the same work (Heft y. p. 44, 
tab. v. f. 2), under the name of Platysomus Althausi, belong also to 
the genus Dorypterus, and to the same species as the one described 
by Prof. Germar. But in order to establish more satisfactorily the 
strict identity of these with the English specimens, it seems neces- 
sary to reproduce the original descriptions given by Prof. Germar 
and Count Munster. 
Dorypterus Hoffmanni, Germar (Heft v. pp. 35-37). “ This 
specimen was found only last autuumn (1840) in the Kupferschiefer 
of the Eisleben district ; and, although it is not perfect enough to 
ascertain all its essential parts, yet it presents so many peculiar 
characters that the establishment of a distinct genus becomes 
necessary. As generic characters one can point out:—an oval profile 
and a body flattened on the sides, with a distinct bony skeleton ; 
avery high and spit-shaped dorsal fin; pectoral fin placed in the 
mid-height of the body, behind the gill-cover ; the small, narrow 
ventral fins in the middle of the ventral margin ; and a fork-shaped, 
equal-lobed tail. 
“‘ The whole length of the fish, from the tail-fin to the front of the 
jaws, is 3 inches 7 lines; its height, without the fins, 1 inch 11] lines; 
the height of the dorsal 2 inches, its breadth in the middle 1 line. 
The head, broadly ovate, has a nearly semicircular outline; the 
under jaws are much bent upwards; and also the front and the nose 
seem much bent downwards. It occupies nearly one-third of the 
