ON DORYPTERUS HOFFMANNI. 243 



X. — On Dorypterus Hoffmanni, Germar, from the Marl-Slate of 

 Midderidge, Durham. By Albany Hancock, F.L.S., and 

 Richard Howse. (Plates IX., X.) 



Within the last few years four specimens of Dorypterus Hoff- 

 manni have been discovered in the Marl- slate of Midderidge, in 

 the county of Durham, by Joseph Duff, Esq., two of them in 

 the year 1865, and the other two in the autumn of last year, 

 1869. A few traces ol other individuals were also observed at 

 the same time and in the same locality. These are, we believe, 

 the first specimens of this very singular fish that have been ob- 

 tained 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. Sedg- 

 wick 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 opportu- 

 nity 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 as- 

 sisted 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 Platy- 

 somus ; 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 dor- 

 sal 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 Miin- 

 ster'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 



