242 Dr. R. H. Traquair on the Structure 
that in the Paleoniscide; but the minute articles of the 
rays are finer and more scale-like, and, as M‘Coy has aptly 
expressed it, present ‘‘a deceptive resemblance to the scales 
of the body.” This view of the structure of the fins of Chei- 
rolepis, however, is denied by Pander, who affirms that the 
apparent joints of the fin-rays are in reality nothing but 
scales which covered internal rays apparently of a flexible 
nature; and such internal non-jointed rays he has actually 
represented tn tab. ix. fig. 2 of his work. Here I feel my- 
self compelled to dissent from the opinion of so high an 
authority as Pander, and to agree with Agassiz and M‘Coy— 
as, in spite of the most careful examination of a large number 
of specimens from various localities, | have never seen any 
thing like the unarticulated rays represented in his figure, and, 
moreover, a transverse section of a small portion of the lower 
lobe of the caudal, from a Cromarty nodule (Pl. X VIL. fig. 6), 
effectually (to my eyes at least) demonstrates the contrary. 
Here the whole thickness of the fin is seen to consist of the 
right and left sets of imbricating demi-rays, no other hard 
parts being visible. And although it is of course not im- 
possible that such internal soft rays may have been present, 
yet the structure as here shown exhibits the most complete 
analogy, or rather identity, with that of the anal fin in Poly- 
pterus and Calamoichthys, in which certainly no other rays 
exist save those whose ganoid, closely jointed, and imbricating 
surfaces are seen on the outside*. 
The shoulder-girdle must next claim our special attention, 
seeing that one of its elements seems to have escaped the 
observation of previous writers, save Powrie, and to have 
been by him completely misinterpreted. Of this the first 
element, by which the arch was attached to the skull, is the 
Jirst supraclavicular, or “ suprascapular” (Pl. XVII. fig. 3, 
Ist s.cl), a small rounded-triangular plate placed immediately 
behind the posterior margin of the cranial shield, and distinctly 
seen only in very few specimens. It is correctly indicated 
by Pander, in tab. ix. fig. 6 of his work, by the number 46. 
Articulated with this is the second supraclavicular (2nd s.cl), 
or “ scapular,” a more elongated plate, broadish above, but 
getting suddenly narrower about the middle, and whose long 
axis points obliquely downwards and backwards to articulate 
* Agassiz was nevertheless inclined to believe that in some species of 
Paleoniscus (e, g. P. Blainvillei and P. Voltzii) the fin-rays were really 
covered with scales (Poiss. Foss. t. 11. pt. 1, p. 43). I do not, however, 
find this idea corroborated by the specimens of Pale@oniscus Blainvillet 
in the British Museum, which I have carefully examined; P. Voltzit I 
have not seen. 
