42 Dr. R. H. Traquair on the 
inclined to refer to G. obliqguus, and in it, near the tip, the 
transverse section has a form much resembling in general 
characters that in M‘Coy’s figure; but one margin of the 
groove is nevertheless a little more prominent than the other. 
It is to be hoped that American paleichthyologists will care- 
fully examine the spines of Gyracanthus occurring in their 
country with special reference to the present question. 
2. The supposed Carpal Bones of Gyracanthus. 
Of constant occurrence in the same beds with G'yracanthus 
spines, and often found closely associated with them on the 
same slabs of stone, are certain peculiar bones, first noticed by 
Messrs. Hancock and Atthey, and by them interpreted as 
“carpal”? bones. These occur of two forms or shapes, the 
first of which was described by the above-named authors in 
1868*. It is a flat triangular bone, with a thick apex oppo- 
site to a thin base; and two other sides, one of which, the 
longer, is slightly convex, the other, or shorter, being straight 
or slightly concave : of the two surfaces one is slightly convex, 
the other slightly concave in general contour. Of. these 
Messrs. Hancock and Atthey say, “Their structure is very 
open; and as they are seldom well preserved, they are pro- 
bably only imperfectly ossified; the bony fibre radiates from 
the apex to the expanded base. ‘There can be little doubt that 
these are carpal bones similar to those in connexion with the 
pectoral fins in sharks and dog-fishes.” 
The second form is briefly noticed by the same authors in 
another communication published four years later, and its form 
is described as follows :—‘‘'T'his second form is probably the 
inner carpal; it is a broad flat bone irregularly bilobed or 
somewhat reniform, with one of the lobes produced and the 
external margin straightened ; the convex border is a little 
flattened, angulated, and thickened, thence the bony fibres 
radiate to the opposite or lobed margin... .. The texture 
of the bone is quite similar to that of the large triangular 
carpal, namely, it is of a semicartilaginous appearance, with 
coarse radiating fibres extending from margin to margin ”’T, 
In other passages Messrs. Hancock and Atthey clearly 
indicate that they considered the thin margin, in both forms, 
to be distal, and the apex, or point from which the “ bony 
fibres ” radiate, to be proximal in original position. 
Before making any critical remarks on the above determi- 
nation of the bones in question, it is necessary to fix accu- 
* Ann. & Mag. Nat. Hist. ser. 4, 1868, vol. i. p. 369. 
+ Ann. & Mag. Nat. Hist. ser. 4, 1872, vol. ix. pp. 260, 261. 
