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



Pleuracanthus Wardi. Davis. 

 (PI. LXXII., fig. 15.) 



Pleuracanthus Wardi, . . Davis, J. W., 1880, " Quart. Journ. Geol. Soc," 



vol. xxxvi., p. 334, pi. xii., fig. 6. 

 Pleuracanthus Wardi, . . Etheridge, R., 1888, " Foss. Brit. Islands." 

 Pleuracanthus Wardi, . . Woodward, A. S., 1889, " Cat. Foss. Fishes Brit. 



Mus.," pt. I., p. 10. 

 Pleuracanthus Wardi, . . Ward, J., 1890, " Trans. N. Staffs. Inst. Mining 



and Mech. Engin.," vol. x., p. 136. 

 Pleuracanthus Wardi, . . Woodward & Sherborn, 1890, " Cat. Brit. Foss. 



Verteb.," p. 155. 



Spine: imperfect; the part jireserved consists of the median part, 0*15 m. in 

 length. The base and upper portion are absent. It is 0*012 m. diameter nearest 

 the base, and diminishes gradually to 0*007 m. at the part preserved nearest to 

 the point. The front of the spine is rounded and striated longitudinally ; the 

 posterior surface is armed with a double row of denticles, forming continuous 

 ridges, and separated only by a narrow groove. The denticulated surface extends 

 a distance of 0*09 m. ; the denticles are short and obtuse, probably due to abrasion. 

 The spine in transverse section is depressed on each side of the lines of denticles 

 towards the median lateral line, which is somewhat angular. The spine is arched 

 towards the posterior surface, and the internal cavity is large in proportion to 

 the size of the spine. 



This spine more nearly approaches the characters of Pleuracanthus cylindricus, 

 Ag., than any other, and it has been suggested by Mr. Ward and others that its 

 separation from that species may be conjectural. After a careful reconsideration 

 of the specimens, however, I am still of opinion that its long slender form and 

 decided curvature, together with the closely approximating lines of denticles 

 forming continuous ridges, and the form of the spine in section, separate it with 

 sufficient distinctness from the stronger cylindrical spine and the well-defined 

 denticular arrangement of P. cylindricus. 



Formation and Localitjj. — Ragmine Ironstone Shale, Fenton, Staffordshire. 



Ex coll. — John Ward, Longton. 



