TRIASSIC FISHES FROM SPITZBERGEN 
201 
Glaucolepis gyrolepidoides n. sp. 
(PI. 25, figs. I, 2). 
Synonym: Gyrolepis ? sp. Stensio, Erik a:son, Norsk Geol. Tidskr. vol. V., p. 77, 1918. 
The present material of G. gyrolepidoides is rather poor and incomplete. The Palae¬ 
ontological Institute of Upsala has in its possesion three incomplete specimens (P. 166, 
P. 671 a, b) and a number of detached scales (P. 5, P. 7, P. 9, P. 27, P. 650, P. 652, P. 656 , 
P. 657, P. 665, P. 667). The Palaeontological Institute of the University of Christiania has 
in its collection, as I have already had occasion to mention (1918 b, p. 77), an incomplete 
specimen from the Ice Fjord and some detached scales from Horn Sound. 
The species in question was probably of medium or fairly small size. To judge 
from specimens P. 671 a and b it has a rather slender body (PI. 25, fig. 1). 
Nothing is preserved of the head and the most anterior part of the abdo¬ 
minal region. 
The skeleton of the unpaired fins. 
The anal fin ( A, PI. 25, fig. x) is small, with a short base and triangular in shape. 
Its lepidotrichia, which are about 20 in number, decrease rather rapidly in height back¬ 
wards and are situated close together. They are jointed throughout their length, and are 
probably also ramified dichotomically in their distal parts. Their lateral sides are covered 
with ganoine. Fulcra are not observed with certainty. 
The dorsal fin (D, PI. 25, fig. 1) is of about the same size and shape as the anal 
fin and its exoskeleton shows in all respects the same conditions as in this fin. It is so 
situated that its posterior half is about opposite the anterior half of the anal fin. The 
fulcra are small but distinct. 
The caudal fin (PI. 25, fig. 1) is fairly weakly developed, deeply cleft, with both 
lobes of about equal strength. If either of these was stronger than the other it was the 
ventral one. The numerous ganoine covered lepidotrichia are dichotomically ramified in 
their distal parts and are closely jointed right to the base. Both here and in the other 
fins the length of the joints is greater than their width. The dorsal lobe has a number 
of enlarged ridge-scales. The anterior margin of the ventral lobe is furnished with 
numerous small fulcra. 
The skeleton of the paired fins. 
The pectoral fins are quite unknown. 
The ventral fins are poorly preserved. They were apparently small and weak 
(F, PI. 25, fig. 1). Their lepidotrichia, the number of which cannot be established, were 
closely jointed throughout their length and presumably dichotomically ramified in their 
distal parts. 
Squamation. 
The lateral surfaces of the body nearest to the head must have had scales that 
were somewhat higher than broad. Otherwise the scales of the whole lateral surface 
are more or less typically rhombic, like those of the back as well. Those of the ventral 
side, on the other hand, especially in the abdominal region and the most anterior part 
of the caudal region, are characterized by their very low shape. Those of the dorsal 
S tensid, Triassic Fishes from Spitzbergen. 26 
