TRXASSIC FISHES FROM SPITZBERGEN 
35 
The mandibulae are strikingly high in relation to the length, as the length was 
about 10 cm and the greatest height about 4. cm. The lower margin is strongly convex 
and passes over without any definite corner into the posterior one. The anterior margin, 
on the other hand, is better defined and passes into the ventral one by means of a 
rounded angle. The upper margin has an obtuse-angled process in front of the articulatory 
fossa, otherwise it seems to have been straight and to have occupied an almost horizontal 
position. In the direction from the anterior to the posterior margin the mandibulae are 
concave on the lateral side and correspondingly convex on the medial side. 
The cartilage in the mandibulae has had a total thickness of about 10 mm. Its 
uncalcified part is in its present state of preservation replaced by calcite. 
Between the two mandibulae there is a paired, long skeleton element which is 
somewhat arched. It seems as if we were concerned here with the ceratohyal (Chjr, 
PL 3 , fig. 16 a). 
A number of poorly preserved cartilaginous fragments, situated between, behind 
and ventrally of the mandibulae, have probably belonged to the gill-arches. 
Dentition. 
The arrangement and shape of the teeth.— 
Specimen P. 107 shows on the left mandibula five 
transversal rows with teeth that are rather well preser¬ 
ved in situ (text fig. 14; PI. 3 , figs. i6a,b). As the most 
anterior of these rows lies rather near the anterior 
edge of the mandibula, it is clear that the space for 
further rows in front of those that are preserved is 
very restricted. We can therefore conclude with rather 
great probability that the total number of transversal rows was at most six. It can¬ 
not be decided with full certainty whether any unpaired symphyseal row was present, 
but it seems very probable that this was the case. 
I have denoted the most anterior of the preserved rows by the letter a f 
the one following behind it by b, etc. (text fig. 14, PL 3 , figs. 16 a,b). 
The tooth-row a is composed of at least 6 teeth, having on an average a length 
of about 10 mm and a maximum breadth of 2—2*5 mm. As text fig. 14 shows, they are 
situated rather obliquely in such a way that their anterior end is nearer the labial 
margin of the jaw than is the case with the posterior end. The tooth nearest to the 
labial margin has the masticatory surface of the crown turned dorsally, the tooth farthest 
from it, on the other hand, has the same surface turned ventrally. The teeth inter¬ 
mediate between these two occupy transitional positions. 
The teeth in row a are fairly strongly bent, so that the masticatory surface is 
convex from one end to the other. The most raised part of the crown is at about the 
middle of the teeth or sometimes a little in front of the middle; the greatest width of 
the crown is also situated at the same place. The anterior half of the crown grows more 
narrow than the posterior half, and the anterior end is therefore rather pointed. An¬ 
other characteristic of the anterior end-part seems to be that is arched towards the 
medial side. 
