TRIASSIC FISHES FROM SPITZBERGEN 
151 
the mixicoronoid have small teeth. The axial skeleton has a well-developed chorda, and, 
at least in the caudal region, ossified neural and haemal arches. From the latter ossified 
parts extend dorsally on both side of the ventral half of the chorda forming a sort of 
hypocentra. The unpaired fins are strong. The caudal fin is strongly heterocercal, deeply 
forked and nearly equilobate. The dorsal and the anal fin with numerous (more than 50) 
lepidotrichia. The endoskeletal radials of the dorsal fin with ossifications in the proximal 
and middle segments; those of the ventral fin have, only posteriorly, separate ossifications 
in the proximal and middle segments; otherwise only a single long ossification in each 
endoskeletal radial, extending from the haemal spines to the lepidotrichia. The anal fin 
opposite at least the posterior half of the dorsal fins. The ventral fins large with a rather 
long base and consisting of a large number (about 50) of lepidotrichia. In all the fins 
the lepidotrichia are unjointed for a short distance proximally; the other parts are closely 
jointed. The ganoine ornament is totally lacking on all of them. The rige scales are very 
powerful on the upper lobe of the caudal fin; fulcra are not known. The squamation 
is reduced except for the dorsal lobe of the caudal fin, where the scales are narrow and 
high and without ganoine. The lateral line of the body was surrounded by fine bone-tubes. 
Little has as yet been ascertained as to the relationship between Birgeria and other 
known genera of Palaeoniscids. It is, howover, presumable that, at least in certain respects, 
Birgeria was more specialized than several of the earlier Palaeozoic Palaeoniscids. 
Birgeria mougeoti Agassiz. 
(PI. 20. fig. 6; PI. 21; PI. 22, figs. 1—3; PI. 23, figs. 1—3; PI. 24, figs. 1, 2.) 
Synonyms; Saurichthys mougeoti , Agassiz, i 844, vol.II, part 2, p. 85; for extensive list of synonyms see Woodward A. S. 
Catalogue of Fossil fishes in the British Mus., part III, 1893, p. 20. 
Detached teeth of this or possibly of a couple of closely related species as well 
are found in several horizons within the Triassic rocks of Spitzbergen (P. i —5, 11, 15, 
Si, 48 , 52, 60 3 , 62S — 624, 626 — 628, 633—634 , 795, 878; some detached teeth in the possession 
of Prof. Salomon of Heidelberg). At the fish horizon there occur not infrequently, together 
with such teeth, more or less well preserved parts of heads (P. 165, 169, 171, 840 — 342, 
345, 348 — 849). In addition there were fairly often found in this horizon remains from the 
abdominal and caudal regions of a large Palaeoniscid fish, which I am unable to refer 
to any species other than B. mougeoti. It is true that I have never found these remains 
(P. 148, 144, 150 — 198, 160 — 164) in connection with teeth or crania of B. mougeoti , 
but the other circumstances of the finds and the size suggest very decidedly that 
they belong to this species. Confirmation of this is afforded to some extent by a large 
Palaeoniscid-like maxilla with typical teeth described by me in an earlier paper from 
the German Muschelkalk (Stensio, 1919). 
B. mougeoti attained a very considerable size. The greatest height of the body 
between the dorsal and the anal fin in specimen P. 1558 was thus no less than 25 cm., 
and a couple of caudal fins (P. ig 3 , 155c) were probably more than 40 cm high from 
the extremity of the dorsal lobe to that of the ventral one. The smallest caudal fin so 
far found is more than 20 cm high. The maxilla from the German Muschelkalk is, I have 
already stated in my earlier description of this, over 18 cm long. Assuming that B. mou¬ 
geoti did not differ essentially from other Palaeoniscids in the shape of the body, we 
