CARBONIFEROUS FISH-FAUNA 
free spines of the second pair are much larger and more elevated, 
the basal extent of each being about one-and-a-half times as 
great as that of the anterior spine, while the height somewhat 
exceeds this measurement. Parts of both of these large spines 
are seen in the type-specimen, that of one side being represented 
solely by its apex, while that of the other side is better displayed 
in several broken surfaces. Another good example is well shown 
in PI. II, fig. 1, and lacks only the apex. A more imperfect 
specimen is seen near the front of the fossil represented in PI. V, 
fig. 1 . This spine is situated opposite and just on the inner side 
of the inserted part of the pectoral fin-spine. Like the smaller 
spine in front, it is a thin- walled, hollow, laterally-compressed 
cone, with its base-line more or less coincident with the long axis 
of the trunk, that is, parallel with the basal edge of the fin-spine. 
Its outer side (PI. II, tig. la) is gently convex, with a sharply- 
bevelled area in front (resembling that of the corresponding spine in 
Gyracanthus and Ora cant hits 1 ) ; its inner side is flattened Or even 
slightly concave, and seems to be emarginate or excavated at its 
basal edge; its posterior aspect (PI. II, fig. 16) indicates the 
amount of the lateral compression. Remains of the actual 
tissue of the spine in the type-specimen show that it was very 
porous, with an appearance of fibres radiating from the apex 
towards the irregularly-crimped base (shown in internal cast in 
PI. II, fig. la). An impression of the outer face in PI. II, fig. 
1 (a) reveals a close ornament of small, rounded tubercles, not 
clearly arranged along the radiating structural lines, which are 
here very conspicuous. These tubercles (PI. II, fig. le) are not 
noticeable in any other specimen, probably on account of the 
state of preservation. They might even be marks of the shagreen 
granules of a piece of skin pressed against the spine in the fossil, 
like the tubercular impressions covering the base of the adjoining 
pectoral fin-spine; but they are more probably true ornament, 
for similar tubercles occur on the corresponding spines both of 
1 J. W. Davis, “ On the Fossil Fishes of the Carboniferous Limestone Series of Great 
Britain.” — Trans. Roy. Dublin Soc. [2], vol. i. (1883), p. 529, pi. lxiii., fig. 1. 
[8] 
