A HISTORY OF DURHAM 



Of ganoids with a more normal, or, rather, .nore speciah'sed, type of fin, our first representation 

 is Pygoptc-rus humholdtl^ a member of the family Palivonhcidts first described on the evidence of 

 specimens from the continental Kupferschiefer, but subsequently identified from the Marlslate of 

 Middridge and Ferryhill. A specimen from the latter locality was regarded by Sir P. Egerton as 

 representing a distinct species, P. latus ; but its peculiarities in shape appear to be due to the effects 

 of crush. 1 This fish has also been called P. mandihular'n. To the same family belongs Palaonhcus 

 frelesleheni, already mentioned under the heading of the Lower Magnesian Limestone, which also 

 occurs in the Marlslate of Ferryhill, Middridge, and East Thickley. A second species of the same 

 genus, P. /onglssimus, was named on the evidence of a specimen from the Clarence Railway cutting, 

 near Mainsforth, in the present county, and also occurs at Ferryhill and Middridge. The type 

 specimen is in the Museum at Newcastle-on-Tyne, but the counterpart is in the collection of the 

 British Museum. A third species, P. rnacrophthalmus, also typically from Durham, occurs at Ferry- 

 hill and Middridge ; the type specimen (a nearly complete fish) being in the Museum of the 

 Geological Society of London. The so-called P. elegans appears to be a synonym of P. freiedebeni. 

 To the same family belongs the genus Acrolepis, already referred to when treating of the fishes of the 

 Lower Magnesian Limestone. It is typified byy^. sedgwlcki, first described from Middridge, and also 

 occurring at Ferryhill ; the continental A. aspcr being apparently referable to the same species. A 

 second species, A. exscu/pta, typically from the German Kupferschiefer, is also recorded from the 

 Marlslate of Middridge and Fulwell Waterworks. 



The family Platysomatida, the members of which, as already said, are distinguished from the 

 Palaonhclda by their shorter and deeper bodies, are represented in the Marlslate of the county by at 

 least two, and possibly by three, species. The first of these is Glohulodus macrurus, a genus and 

 species typically from the German Kupferschiefer differing from the better known Mesohph of the 

 Coal Measures by the dentition. This fish occurs both at Middridge and Ferryhill. Of the typical 

 genus P/atysomus, the aforesaid P. gibbosus (also known as P. striatus) occurs at the two localities 

 last named. 



Perhaps the most remarkable of all the Marlstone fishes is the one described from the German 

 Kupferschiefer as Dorypterus hoffrnannl, of which the serial position is still problematical. According 

 to Messrs. Hancock and Howse, by whom they were described, four examples of this singular fish 

 have been discovered at Middridge, two in 1865 and two in 1869 ; all four being in the Newcastle 

 Museum. The genus takes its name from the presence of a sword-like dorsal fin, recalling in form 

 (although not in structure) the back-fin of a killer-whale. Dr. Smith Woodward^ observes that : — 

 ' This fish still requires satisfactory elucidation, but it is evidently related to the P/atysomatida, as indicated 

 by the great development of the azygous [unpaired] fin-supports, which are sometimes, at least in 

 part, mistaken for dermal structures. So far as the absence of flank-scales is concerned, Dorypterus 

 bears the same relation to the typical Platysomatidie as Phanerosteon with respect to the typical 

 Palceonhcida.' 



Lastly, in the family Semtonotid/e we have a species of the genus Acentrophorus, already referred 

 to under the heading of the Lower Magnesian Limestone, in the Marlstone of the county. This 

 species, A. glaphyrus, was named by Agassiz on the evidence of a Durham specimen preserved in the 

 York Museum. It differs from the type species by the conspicuous serration of the scales. There 

 are specimens of this fish from Middridge and Ferryhill in the collection of the British Museum. 



Although remains of fishes are far from uncommon in the Northumberland Coal Measures, 

 hvf appear to be recorded from the Carboniferous rocks of Durham, none being mentioned by 

 Mr. Howse in his catalogue of the collection in tlie Newcastle Museum. The present writer has, 

 however, been informed by a local authority that such remains are quite common in the Durham 

 Coal Measures, more especially in the slialey layer capping the Hutton seam. They have never 

 yet been collected systematically, although they are probably quite as numerous as in the hard main 

 shale at Newsham, Northumiicrland (wliich is the same bed as tlie Hutton scam), where tiiey were 

 assiduously collected by the late Mr. Atthcy. 



One species of fossil fish, the primitive pavement-toothed shark Pctalodus aaiminatui^ is recorded 

 from the Upper Carboniferous Limestone of the county by Dr. A. Smith Woo.lward in the 

 (catalogue of Foail Fishes in the British Museum.^ Since, moreover, in the same work* the widely 

 spread fringe-finned ganoid Mrgn/ichthys /'//'/'c/// is stated to be known from all the English Coal-fields, 

 its remains probably occur within tlie limits of the county under consideration. 



' Sec Cfjt. Foss. Fish. Brit. Miis. ii. 474. 

 ' Cat. Foss. Fiih. Brit. l\Jus. ii. 550. 8 i. 41. * ii. 380. 



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