714 Davis — On the Fossil Fish-Remains of the Coal Measures of the British Islands. 



found associated in a single Jaw are so divergent in form that specific distinction 

 of isolated examples becomes quite problematical. The spines certainly offer 

 more persistent and better defined characters than the teeth. A comparison 

 of the figures of the teeth in the fine series of specimens it is now proposed 

 to describe from the Newcastle coal field will confirm this view. Had all the 

 teeth been obtained as individual specimens they might reasonably have served 

 for descrijjtion as different species. Notwithstanding these difficulties, the 

 occurrence of numbers of apparently well-defined and jjersistent forms, some- 

 times found only in one locality and stratum, and in others characteristic of 

 several localities, renders necessary their description as separate species. 



In addition to the isolated specimens of spines and teeth there have been 

 found masses of shagreen, with an occasional well-preserved archipterygial fin, 

 or single specimens of spinous or interspinous processes, in the Coal Measures of 

 the West Riding of Yorkshire ; but the most valuable and interesting series of 

 specimens has been discovered in the Lowmain coal seam at Newsham, in 

 Northumberland, and is contained in the Atthey collection, recently purchased 

 by Lady Armstrong, and placed in the museum at Newcastle-on-Tyne. From 

 the same locality, a second collection, containing most remarkable examples, has 

 been acquired by Mr. William Dinning, of Newcastle. Examples from both 

 collections are described in the following pages. The fishes varied very much 

 in size, from an example measuring neai'ly half a metre across the head and 

 with a possible length of three or four metres, to a head represented by the 

 exquisitely preserved cranium in the possession of Mr. Dinning, which has a 

 diameter of only one-tenth of a metre. The latter specimen is the only one 

 found on this side the Atlantic exhibiting a cranium in which the several 

 elements are separated by sutures. The beautiful series of examples found in 

 Bohemia and described by Dr. Fritsch ; or those equally well, or perhaps better, 

 preserved found at Commentry, in France, and described by M. Chas. Brongniart, 

 exhibit the cranium only as a mass of cartilage without segmentation. The 

 fossil remains described by Professor Cope as " Didymodus," obtained from the 

 Permian beds of Texas, possessed crania which showed the comijonent parts 

 forming a continuum displaying distinct segments. The example in the collection 

 of Mr. Dinning exhibits the surface configuration of the cranium with great 

 clearness. 



The upper and lower jaws are exhibited, in relative position to each other, 

 in a very fine specimen at the museum at Newcastle. The specimen was 

 excavated and developed by the late Mr. Atthey. On one side of the slab the 

 two lower jaws are preserved, with large cranial jolates lying near, and on the 

 opposite side the upper jaws are exposed, with numerous teeth, as well as the 

 reverse sides of the plates exhibited with the lower jaws. This specimen probably 



