woodward: fossil fishes of the upper lias of WHITBY. 469 
are constricted, then more sharply turned backwards, and 
slightly expanded at their truncated distal end. 
The clavicle has been already mentioned in the large group 
(pi. Ixviii., fig. 1, cl.), but a still finer specimen is represented 
from the outer aspect in the accompanying fig. 9. This bone 
is identical in shape with the corresponding element both in 
Chondrosteus and in the sturgeon (fig. 10). The supraclavicle 
has also been identified in the large group ; but another 
characteristic example, wanting the inferior process, is perhaps 
more clearly represented from the inner aspect in fig. 11. 
As might be expected, the fins are 
very imperfectly known. One fragment 
in the British Museum (No. P.3356n) 
comprises a series of un jointed rays, the 
longest piece preserved being 0-5 m. 
in length ; it may have been part of 
the pectoral, but its exact position in 
the fin-skeleton cannot be determined. 
It clearly formed an anterior margin, 
and its rays gradually increase in length 
backwards, terminating successively at 
the border. The two parallel rods of 
which each ray is composed are fused 
together at the pointed distal end. 
Most fragments of the fins of Gyrosteus^ 
however, exhibit very closely articulated 
rays ; and a good example, which pro- 
bably belongs to the tail, is shown in 
fig. 12. In this specimen the rays are 
un jointed for a short distance at their 
inserted end, but they soon become 
crossed by closely-arranged sutures, and 
nearer their extremities they bifurcate 
once or twice. It may be added that 
one small fin in Mr. Samuel Chadwick's collection in the Malton 
Museum, probably a pectoral of Gyrosteus, exhibits the minute 
Fig. 11. — Gyrosttm mirahilis 
Ag., MS.; right supra- 
clavicle, inner aspect, 
one-sixth nat. size. [Brit. 
Mus., Xo. P. 33566.] 
