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) accurately described the position of this quarry and the stratum 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 specimen, 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 opinion 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 identify Mr. Duff's discovery with the Dorypterus Hoffmanni described originally by Prof. Germar in Count Minister's Beitrage zur Petrefactenkunde (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 Munster in the same work (Heft v. p. 44, tab. v. f. 2), under the name of Platysomus Althausii, 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 necessary 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 autumn (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 ; a very 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
