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



The spine of Plenracanthus (Fiber (jensis, Fr.,* is very much like the medium- 

 sized species of P. Icevissimus, Ag., from the Coal Measures near Glasgow. They 

 are the same length, and each side of the spine is armed with about forty 

 denticles. The spine of Xenacanthus Decheni, Goldf.,t also resembles P. Icevissimus, 

 Ag., both in form and size, and the number of denticles in each is the same. 



Formation and Locality. — Lowmain Coal Seam, Newsham, Northumberland; 

 Cannel Coal, Tingley ; Better-bed Coal, Yorksliire ; New Ironstone (Ragmine) 

 Fenton ; Arley Mine, Burnley ; Shattleston, near Glasgow. 



Ex coll. — Museum of Natural History, Newcastle-on-Tyne ; J. W. Davis, 

 lifax ; John Ward, Longton ; Jamej 

 castle-on-Tyne ; George Wild, Bardsley 



Halifax ; John Ward, Longton ; James Thomson, Glasgow ; W. Dinning, New- 



Pleuracanthus robustus, Davis. 

 (PI. LXXII., figs. 10-14.) 



Pleuracanthus robustus, . . Davis, J. W., 1880, " Quart. Journ. Geol. See," 



vol. xxxvi., p. 330, pi. XII., fig. 5. 

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

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



Mus.," pt. I., p. 7. 

 Pleuracanthus robustus, . . Ward, J., 1890, " Trans. N. Staffs. Mining and 



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

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



Verteb.," p. 15-5. 



Spines : the largest examples occur at Tingley ; they are imperfect, the base 

 being absent. The joart preserved is 0'09 m. in length ; if perfect it would pro- 

 bably have measured O'll m. The surface is covered with fine longitudinal 

 striations. The diameter in the median part is 0*008 m., whence it tapers to a 

 point at the distal extremity. The basal extremity is also considerably less in 

 diameter than the median part. An internal cavity occupies rather more than 

 one-third the diameter at a distance of 0"09 m. from the point. The spine is very 

 slightly curved. In section the superior surface is rounded in the upper half, and 

 more or less triangular nearer the base ; the inferior surface is slightly curved, and 

 forms a longitudinal median ridge. The angles formed by the outer edges of this 



* Op. cit., p. 15, pi. xcvi., fig. 3. 



f Beit. Vorwelt Fauna, p. 23, pi. y., fig. 9, 1847 ; and Fritsoh, op. cit., pi. xctiii., fig. 2. 



