TRIASSIC FISHES FROM SPITZBERGEN 
23 
As in the Liassic species of the genus in question A. oppenheimeri may probably 
have had two or three transversal rows among the middle ones which consisted of long 
and robust teeth. That this was the case is clearly shown by the comparatively con¬ 
siderable number of such teeth that are present in the material of the fish hitherto 
found. The largest of these teeth have a length of 3 o —33 mm, the smallest about 
21—25 mm. The greatest height varies between 7 and 10 mm, and it is often as great in 
the shorter teeth as in the longer ones. One finds also not infrequently that the former 
are somewhat wider than the latter. Seen from the medial and lateral, side (PI. 3 , figs. 6, 
8 b, c, 9, 10), i. e. in the vertical plane through the axis of length, they are arched 
in such a way that their distal outline is convex and the basal one correspondingly 
concave. Often, however, this curvature is not strongest at their middle, but some¬ 
what to the side of this towards one end, and in such cases the highest part of the 
crown is consequently situated asymmetrically. Certain teeth show in addition curvature 
in the horizontal plane in such a way that their middle part is convex at the medial 
side and correspondingly concave at the lateral side, while their end parts show quite 
contrary conditions (PI. 3 , figs. 8 a, 10). 
In the great majority of these larger teeth the crown is long and low (text figs. 7, 
8; PL 3 , figs. 6, 8, 9, 10). On several of them its width is fairly small and in several 
cases it is almost the same from one end to the other (PL 3 , fig. 10). The narrowing 
towards the ends is, however, always continuous and gradual, 
so that there are no sudden contractions or similar appearances 
of the breadth of the crown, as is often the case in the type 
of teeth described in the literature under the name of 
A. gaillardoti. 
The crown has no trace of cones. Its highest part is 
always well rounded, has never any marked angle, and, as 
has already been pointed out, is often somewhat asymmetri¬ 
cally situated towards one end. 
The sculpture is rather similar on all the larger teeth in question. A longitudinal 
crista, which may either occupy a median position or may be situated more or less to 
one side, is always developed. On the other hand a transversal crista is quite absent. 
Numerous striae issue at right angles on both sides of the longitudinal crista. Every 
second or every third one of these is very short, fairly straight and always unramified, 
The others are long, weakly sinuated, and send out fine branches, often directed 
obliquely and basally. The majority of them also extend right to the basal edge of 
the crown both on the lateral and the medial side. On the lateral side they are not 
infrequently thickened close to this edge. — Sometimes on certain of the shorter teeth 
belonging to this category one can find a certain indication of a radiating arrangement 
of a number of striae on the highest part of the crown, and at the same time the rest 
of the sculpture somewhat resembles that of the most anterior teeth. 
On the medial side the crown forms with the root a notch, often rather strong 
(text figs, 7 A, B, C). In most cases the root is probably at least somewhat narrower 
than the crown and is strikingly high in relation to the latter. Its basal surface does 
not seem to be oblique on the few teeth in which it can be observed. 
"0 V V 
Text fig. 7. 
Acrodus oppenheimeri n. sp. 
Cross-section through teeth from 
the middle transversal rows. Medial 
side to the right. A, through the 
tooth belonging to State Museum, 
Stockholm; B and C, two teeth 
from specimen P. io 5 . V.. 
