704 Davis — On the Fossil Fish-Remains of the Coal Pleasures of the British Islaiids. 



Amongst the owners of private collections I ara greatly indebted to my friends 

 and co-workers, James Thomson, Esq., of Glasgow ; Dr. J. R. S. Hunter, of Carluke, 

 and R. Dunlop, Esq., of Airdrie, in Scotland; George Wild, Esq., of Bardsley, 

 and James Nield, Esq., of Oldham, in Lancashire ; Professor Louis C. Miall, of 

 the Yorkshire College, and T. W. Embleton, Esq., of Methley, in Yorkshire ; 

 to William Dinning, Esq., of Newcastle, an able palseontologist, to whose manipu- 

 lative skill science is indebted for some of the most beautiful examples figured 

 in the present monograph, I owe many thanks. No worker in this branch of 

 palseichthyology can afford to do without the assistance of John Ward, Esq., of 

 Longton, in Staffordshire ; his great collection, unique in many respects, and the 

 result of many yeai-s of j^atient investigation, is invaluable ; and to this collection, 

 and the practical knowledge possessed by Mr. Ward, willingly placed at my disj)0sal, 

 I am under deep obligations. And lastly, to A. Smith Woodward, Esq., whose 

 fellowship is very dear to me, I am indebted for many helpful courtesies and 

 kindnesses, which may perhaps be more easily understood than expressed. 



II.— CLASSIFICATION AND DESCEIPTION. 



Class.— PISCES. 



Sub-Class I.— ELASMOBRANCHIL 



Order I. — Ichthyotomi (E. D. Cope and A. Smith Woodward). 



Spi. — Xenacanthidse, H. B. Geinitz, C. F. Liitken, Anton Fritsch ; Pteryga- 



canthidse, Cli. Brongniart. 



Endoskeletal cartilage permeated throughout with granular calcifications ; 

 notochord rarely or never constricted ; calcifications of the sheath arrested at 

 the most primitive rhachitomous stage, except in the caudal region. Neural and 

 haemal arches and spines long and slender ; with or without intercalary cartilages. 

 Pectoral fins with long segmented axis (archipterygium). 



Family. — PLEURACANTHIDiE. A. Smith Woodwaed, Ch. Beongniart. 



Si/n. — Xenacanthidse, Anton Fritsch. 



Body slender, but slightly depressed ; mouth terminal ; tail diphycercal ; dorsal 

 fin elongate, low, continuous along the back from a point shortly behind the head ; 

 slender interneural cartilages more numerous than the neural spines. Pectoral fin 

 with biserial arrangement of cartilaginous rays. 



