534 On the Fossil Fishes of the Carbomferous Limestone Series of Great Britain. 
Phoderacanthus grandis, Davis. 
(Pl. LXV., fig. 1.) 
Oracanthus pustulosus—MS. in Collection of the Earl of Ducie. 
Spine, very large, massive and strong, gracefully arched, devoid of posterior 
cavity, or external groove. Imperfect at the basal extremity and exhibits no 
basal surface indicating the extent of its insertion in the integument of the body. The 
length of the part preserved is 27 inches; the diameter near the base is 5 inches, 
it gradually decreases towards the apex ending in a point. The surface of the 
spine is much fractured and broken, but sufficient remains intact to show the 
nature of its ornamentation. Transverse section more or less oval, inferior margin 
rotund, lateral ones convex, gradually converging to form a superior margin 
slightly less rotund than the inferior one. Near the apex the section is much less 
compressed than it is near the base, the latter appearing to be somewhat crushed. 
The internal cavity is large and conforms generally to the external surface. The 
walls of the spine are about ‘5 of an inch in thickness, except on the superior 
margin where they are somewhat thicker. The surface of the spine has been 
uniformly ornamented with a series of pustulate ridges, extending in longitudinal 
rows; the pustulations also extend in close lateral contiguity one with another 
forming a continuous, somewhat wavy ridge across the spine, less regular and 
slightly smaller near the apex than below. The pustulations are smooth, prominent, 
broadly and firmly implanted in the body of the spine. There is no distinct 
evidence of either superior or inferior margin having possessed any denticular 
processes larger than the pustulations occupying the general surface. 
The osseous substance of the spine is hard, compact and fibrous. It is pierced by 
longitudinal cylindrical canals which appear to have served the purpose of conveying 
the nutrient juices from the base towards the apex of the spine. The most 
prominent and largest of these canals is situated midway between the external 
surface of the superior margin and the large internal cavity ; it is 1 of an inch in 
diameter; others occur in the substance ef the spine, along the lateral margins 
and may be distinctly recognised in several places where a portion of the outer 
surface of the spine has been removed. 
M. de Koninck, in the description of Antacanthus insignis, Dewalque, from the 
black limestone of Liege (‘‘Fauna du Calcaire Carb. de la Belgique,” p. 74), notes the 
passage of a cylindrical canal in that species similar to the one described above in 
the superior portion of the spine, but he does not mention others. 
Formation and locality: Mountain Limestone, Bristol. 
Fx coll. Earl of Ducie, Tortworth Court. 
