260 _ Dr. R. H. Traquair on Fossil Fishes 
scales of the flank, are subparallel and run more or less verti- 
cally down the scale, or between the two acute angles (fig. 9) ; 
on the scales of the back, however, they often follow a more 
irregular and flexuously contorted course (fig. 11). 
The general contour of the fish, too, as shown in the figure 
illustrating my previous paper, differs considerably from that 
in Pygopterus. In such typical Pygoptert as P. mandibularis 
or P. Humboldt, both dorsal and anal fins are placed much in 
front of the caudal; the dorsal is not particularly large for the 
size of the fish (in fact none of the fins are, save the caudal, 
which is truly tremendous) ; but the base of the anal is pecu- 
liarly extended backwards. On this latter peculiarity Agassiz 
dwells particularly in characterizing the genus; for he says, 
‘‘mais ce qui caractérise plus particulitrement les Pygopterus, 
cest qu’a cette caudale inéquilobe se joint une anale fort longue 
qui garnit le bord inférieur du corps sur une grande étendue’’*, 
In Nematoptychius Greenockii, on the other hand, the dorsal and 
anal are considerably larger in proportion, and placed nearer 
the tail, and the anal fin may be said to be the exact counter- 
part of the nearly oppositely placed dorsal. Other fishes have 
indeed been named “‘ Pygopterus,” in which the peculiar cha- 
racter of the anal fin referred to is also absent, as, for example, 
in the very imperfectly known P. Bucklandi of the Burdie- 
house Limestone, of which Agassiz says that it is characterized 
by having its anal “ trés-rapprochée de la caudale”’ f. What- 
ever value, however, we may be inclined to place on the form 
and position of these fins in a more extended revision of the 
genus Pygopterus, the form of the scales alone is certainly 
abundantly sufficient to distinguish Nematoptychius generically, 
not only from Pygopterus, but from all the other known genera 
of the family of Paleoniscidee. 
In my former communication the teeth were imperfectly de- 
scribed, it being very difficult to obtain satisfactory views of 
them in the Wardie specimens, owing to the hardness and 
peculiar nature of the ironstone in which they are enclosed. 
Specimens from Loanhead, however, preserved in soft bitumi- 
nous shale or in cannel coal, afford better opportunities for 
studying their configuration (Pl. XVI. fig. 8). They are 
acutely conical, round in transverse section, and more or less 
curved inwards. ‘Their apices very distinctly display the well- 
known “enamel cap” clearly marked off on the exterior of the 
* Poissons Fossiles, t. ii. pt. 2, p. 74. 
+ 1b. p. 77. I cannot refrain from expressing very considerable doubts 
as to that species, or, in fact, any other of the so-called Carboniferous 
“ Pygopteri,” being really referable to that genus. 
