/. — Pleuracanthidce . 735 



arcuaius, Newb.,t is a spine closely allied to the one now described. It was found 

 associated with, and buried in, an "ill-defined mass of granular material, which 

 represents in the cannel coal the partly- ossified cartilage that composed the hard 

 parts of the head of Diplodus. With them are also groups of Diplodus teeth still 

 attached to the jaws." The spines were arched and tapering, and striated on the 

 surface, and the posterior face flattened, or raised into a low ridge along the 

 median line, and on each side of it a row of closely set acuminate depressed 

 hooks. The hooks or denticles of the Linton species are apparently longer and 

 more numerous than those from the Better-bed coal, but they closely resemble the 

 Tingley specimens, especially in the striation of the surface of the spine. The 

 Linton spines are from cannel coal. 



P. denticulatus has been found in the Lowmain coal seam at Newcastle. A 

 specimen almost perfect is 0"085 m. in length : the denticulated posterior surface 

 extends from the apex 0'04 m., and is armed with a double row of barbs, about 

 forty in number, on each side. The basal half of the spine is uniform in diameter, 

 except quite near the base, which is smaller. The surface is covered with minute 

 longitudinal strise, similar to that of the Yorkshire specimens (fig. 19). 



A specimen in the collection of Mr. George Wild, from the shale above the 

 two-feet coal at Bardsley, in Lancashire, is identical with this species. The base 

 of the spine is not preserved, the upper portion is slightly arched backwards, and 

 a row of denticles, about forty in number, are exposed, extending a distance of 

 0'05 m. from the point (fig. 20). 



Formation and Locality. — Bone-bed, Better-bed Coal, Clifton and Lowmoor ; and 

 Cannel Coal, Tingley, in the West Riding of Yorkshire ; Lowmain Coal, Newsham, 

 Northumberland ; Two-feet Coal, Bardsley, Lancashire. 



Ex coll. — James W. Davis, Halifax ; Museum of Natural History Society of 

 Northumberland and Durham, Newcastle-on-Tyne ; Greorge Wild, Bardsley. 



Pleur acanthus Howsei, sp. no v. 

 (PI. LXXII., fig. 21.) 



Spine: length, 0-12 m.; diameter, 0-006 m., near the base, from which the 

 diameter gradually diminishes and terminates in a finely-pointed apex. Spine is 

 slightly curved, more or less ovoid in section, with a double row of denticles 

 extending along the posterior surface; from the distal extremity the denticles 

 extend a distance of 0-05 m. The denticles are twenty-eight in each row; short, 



t PalaBont. Ohio, vol. i., p. 332, pi. xi,., fig. 4, 1873. 



TiiANS. EOT. DUB. SOC, N.S. TOl. JT., PAST XTV. 5 P 



