TRIASSIC FISHES FROM SPITZBERGEN 
233 
on the scales towards the dorsum either. On the scales of the ventral side they number 
two or three, on the other scales probably only one, and sometimes at least this single 
stria may be subdivided into a row of somewhat lengthened tubercles. 
As is clearly seen the scale sculpture in the present species has many features in 
common with that of the Boreosomus species and among them specially with B. arcticus. 
* 
Remarks. — Acrorhabdus bertili is, as we shall see, distinctly separated from the 
two other species belonging to the same genus by the scale sculpture. 
The species name bertili is given to the present species after Dr. Bertil Hogbom, 
who, as has been partly mentioned above, has published a number of valuable geological 
work^ on Spitzbergen and has brought back fine collections of fossils, among which the 
vertebrates from the Triassic occupy a very prominent place. 
Geological occurrence and localities. Acrorhabdus bertili is known 
only from the fish horizon. The two type specimens P. 172 and P. 174 come from the 
shore south of Sassen Bay and from Mt. Trident respectively. The doubtful specimens 
were found at Mt Andersson. 
Acrorhabdus asplundi n. sp. 
(PL 3.0,'figs. 1, 2.) 
Only one specimen (P. 173) of this species has been found so far, and this is 
incompletely preserved in many respects. The specimen has been of about the same 
shape and size as the type specimen of Acrorhabdus bertili or perhaps somewhat larger. 
The state of preservation does not enable us to establish anything as to the general 
shape of the body. 
Visceral skeleton. 
The mouth is large, extending, as in the majority of Palaeoniscids, backwards far 
behind the orbit. 
The maxillary (Mx, text fig. 76; PI. 3 o, fig. 1) is large and long and widened to a 
plate behind the orbit. In shape this postorbital part is fairly low and triangular, with 
one margin turned ventrally, one antero-dorsally, and one postero-dorsally; of these 
margins the last-mentioned one is on the whole weakly convex, while the two others 
are weakly concave. 
The mandible (text fig. 76; PI. 3 o, fig. 1) seems to have been rather strong and 
high, at least in its posterior part, which alone is preserved. Its upper margin is straight 
and is without any coronoid process. Of the bones there are only fragments of the 
dentalo-splenial (De) and angular (Ang). 
The preoperculum (Po, text fig. 76; PI. 3 o, fig. 1) is a strikingly wide, triangular 
plate and not, as is most often the case, a narrow, arched bone, consisting of two limbs. 
Of its margins the shortest, which was probably weakly concave, is turned towards the 
orbit, while the longest one, which is convex, faces dorsally and backwards and comes 
into contact with the operculum, the suboperculum, and the nearest following branchio- 
stegal radius ventrally of the suboperculum. The remaining margin, which is weakly 
S ten si 6, Triassic Fishes from Spitzbergen. 3o 
