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



blunt, about their own diameter apart. The two rows are comparatiyely close 

 together. The base of the spine is preserved ; it is hollow, with thin tapering 

 walls. The cavity appears to have been terminal. The surface of the spine is 

 finely striated. 



This spine, which it is suggested should be specifically designated Pleura- 

 canthus Howsei, may be distinguished from P. denticulatus, Davis, to which it 

 bears a general resemblance, by the smaller number of its denticles — it having 

 twenty-eight, whereas P. denticulatus has forty-five on a spine somewhat smaller 

 than the one now described. The denticles in this species are blunt and rounded, 

 in the other they are long, recurved and acuminate. 



Formation and Locality. — Lowmain Coal Seam, Newsham, Newcastle-on-Tyne. 



Fx coll. — Museum of the Natural History Society of Northumberland and 

 Durham, Newcastle-on-Tyne. 



Pleuracanthus alatus, Davis. 

 (PI. Lxxiii., figs. 5-13). 



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



vol. xxxvi., p. 329, pi. xii., fig. 4. 

 Pleuracanthus alternidentatus, Davis, J. W., 1880, loc. cit., p. 328, pi. xii., fig. 3. 

 Pleuracanthus attenuidentatus, Etheeidge, R., 1888, " Foss. Brit. Islands," pt. i., 



p. 337 (misprint). 

 Pleuracanthus altus, . . Etheridge, R., 1888, loc. cit., p. 337 (misprint). 

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



Mus.," pt. I., p. 9. 

 Pleuracanthus alternidentatus, Woodward, A. S., 1889, loc. cit., p. 9. 

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



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

 Pleuracanthus alatus, . . Woodward & Sherboen, 1890, " Cat. Brit. Foss. 



Verteb.," p. 153. 

 Pleuracanthus alternidentatus, Woodward & Sherboen, 1890, loc. cit., p. 153. 



Spine: length, 0'07m. ; breadth, 0"005 m. ; straight; diameter greatest in the 

 middle and diminishing towards each extremity, the upper one ending in a point. 

 In section the posterior face forms a depressed curve ; the anterior one is semi- 

 cii'cular ; along the angles formed by the two there extends, for about one-third 

 the length from the apex, a double row of denticles, varying in number from seven to 

 ten on each side. The denticles are broad at the base, connected one to another 



