PALAEONTOLOGY 



horizon is a split slabof yellow limestone showing the skeleton of the trunk and part of the skull of a four- 

 limbed air-breathing vertebrate, for which the name Lepidotosaurus duffi has been proposed by Messrs. 

 Hancock and Howse.' The slab with the skeleton itself is preserved in the local Natural History 

 Society's Museum at Newcastle-on-Tyne, and the counterpart, displaying the impression of the 

 same, in the British Museum. The specimen was obtained in 1867 from a quarry at Middridi;c, 

 near Bishop's Auckland. By its describers Lepidotosaurus was referred to the primxval salamanders, 

 a group technically known as Labyrinthodoiitia or Stcgocephalia, and typically characterised by the 

 complete roofing of the skull, the sculpturing of the cranial bones and of those forming the 

 characteristic chest-shield, the complex internal structure of the teeth, and the presence of an armour of 

 bony scales on the lower surface of the body. Such scales are present in the Middridge skeleton, and 

 serve to indicate that the original determination is probably correct, although, from the imperfect 

 condition of the specimen, the exact serial position of the genus cannot be determined. 



The fishes of the Lower Magnesian Limestone of the county appear to be two in number, 

 Paltroniscus fre'uslebeni and Platysomus gihbosus, the two genera to which they belong respectively 

 typifying the families PaLronisddie and Platysomatida:. Both families belong to the enamel-scaled 

 group J the members of the former being characterised, among other features, by their slender 

 herring-like shape, while those of the latter are deeper-bodied, rhomboidal fishes, more like a John 

 Dory in contour. Both species occur typically in the Kupferschiefer, or Upper Permian, of 

 Thuringia. Of P. freieslebtn't the Durham examples from the Lower Limestone were obtained at 

 Down Hill, near Boldon, Houghton-le-Spring ; while those of P, gihbosus came from Pallion Quarry, 

 near Sunderland.* 



Next in order comes the Marlslate — the equivalent of the German Kupferschiefer — which, 

 although a very thin and local deposit in the county, has yielded some very interesting fossils. 



The most important, perhaps, of these are two slabs from Middridge, now preserved in the 

 Museum at Newcastle, each of which displays a portion of the skeleton of a reptile of the size of a 

 large lizard. These specimens were described and figured by Messrs. Hancock and Howse,' by 

 whom the one was referred to Protorosaurus * speneri, a primitive reptile from the German Kupfer- 

 schiefer, while the other was made the type of a second species of the same genus, with the title of 

 P. huxleyi. The Protorosaurida form an extremely generalised group of early reptiles whose nearest 

 existing representative is to be found in the New Zealand tuatera [Sphenodon punctatus), which 

 typifies the order Rhynchoccphalia. At present, they are the earliest known members of the 

 reptilian class. Two species, P. speneri and P. /incii, are known from the Continent, the first of 

 which is, as above stated, recorded from Durham. P. huxleyi is unknown elsewhere than in 

 Durham. 



Fish-remains from the Marlslate of the county are much more numerous. Among these, 

 mention may first be made of the widely spread primitive shark known as Janassa bituminosa, 

 typically from the German Kupferschiefer, but of which teeth have been discovered at Middridge. 

 These teeth, as in other representatives of the Petahdontidtt^ formed a pavement when arranged in 

 the mouth ; the number of rows of principal teeth in this particular genus being three. From the 

 evidence of Durham and Northumberland specimens, Messrs. Hancock and Howse ' formulated a 

 scheme of the mode of arrangement of the teeth, from which they were led to believe that Janassa 

 was a ray. Their interpretation was, however, shown by the late Professor K. von Zittel to be 

 incorrect. Another shark, fVodnika althausi (also known as IF. striatula), belonging to the same 

 family [Cestraciontidee) as the existing Port Jackson shark, is recorded by Mr. Howse from the Marlslate 

 of East Thickley Quarry. The species, which is the only member of its genus, is typically from the 

 Kupferschiefer of Thuringia ; and the genus is distinguished from the Port Jackson shark {Cestracion) 

 by all the teeth, which are large size, being of a crushing type, and by the small number of those 

 in the front of the jaws. Although the species is included in Messrs. Woodward and Shcrborn's 

 British Fossil Vertebrates^ it is not given as British in the Catalogue of Fossil Fishes in the British 

 Museum.* Of the enamel-scaled, or ganoid, fishes from the Durham Marlslate, the first is 

 Ctelacanthus granulatus, the typical representative of a genus and species founded by Agassiz on a 

 specimen (now in the British Museum) from Ferryhill, but likewise known from Fulwell Hill and 

 Middridge, and also occurring in the Thuringian Kupferschiefer. The genus belongs to a separate 

 family {Calacanthidtt) of fringe-finned ganoids, now represented by the bichcrs and the reed-fish of 

 the African rivers. The specimen from Ferryhill described in 1850 by Sir Philip Egerton as a 

 distinct species under the name of C. caudalis is now ascertained to pertain to an immature example 

 of C. granulatus. 



I Nat. Hilt. Trans. Northumb. and Durham, iv. p. 219, pt. viii, and ^art. Joum. Geo/. Soc. xivi. 556, 

 pt. 38 (1870). » Fide Howse, Nat. Hist. Trans. Northumb. and Durham, x. 247. 



* Sluari. Joum. Geo/. See. xxvi. 565, pis. 39 and 40 (1870). 



♦ The name (as was usual at that time) is spelt Proterosaurus. 



' //»«. Mag. Nat. Hist. (4) v. 47 (1870). » i. 248. 



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