TRIASSIC FISHES FROM SPITZBERGEN 
specially mention Day (1864, pp. 57—65), Eck (1865, pp. 60—62, 116—118), Jaekel (1889, 
pp. 3 io—329; 1898, p. 145), v. Meyer (1849 b, pp. 229—233), Plieninger (1844, pp. 115—117), 
Sauvage (i883,pp.4g3—494), Schmid (1861, pp. 15—18), and Woodward (1889a, pp.279— 3 o 6 ). 
The material at Agassiz’s disposal consisted practically entirely of detached teeth. 
Only a couple of fragments of jaws with a number of teeth in situ seem to have been 
known to him. Although the finds made after his time have thrown some new light on 
the organization of these sharks, still our view about them is very incomplete. Remains 
of Acrodus species are certainly not infrequent in several horizons of the mesozoic 
formations in Europe (cf. Woodward, 1889a, loc. cit.; de Alessandri, 1910, pp. 34—-35; 
Zugmeyer, 1875, pp. 79—80), but the state of preservation of these remains, as we know, 
makes it impossible in most cases to study them in detail and in many cases even does 
not permit of any certain determination. 
Agassiz considered that there was a close relationship between Acrodus and the 
recent Cestracion, for which reason he included Acrodus among his «Cestraciontes», 
while Hybodus was put in another family. This view was for a long while the prevailing 
one and it is still found as late as in Zittel’s *Handbuch» (1887—1890, pp. 67, 76). 
There had however been earlier authors (Charlesworth, i 83 g, p. 245; Owen, 1845, p. 57; 
Mackie, i 863, p. 243) who maintained that Acrodus ought to be connected with Hybodus, 
but it can scarcely be said that any proof of this was put forward before Day (1864, 
pp. 63 —65). More recent investigations, especially those of Woodward and Jaekel, have 
now fully made it clear that this latter view is the correct one. — Jaekel has also 
pointed out the relations between Acrodus on the one hand and the genus Polyacrodus 
founded by him on the other (1889, pp. 321—324). 
The genus Acrodus is known with certainty earliest in the Triassic*) and in the 
definition given it by Woodward it seems to have persisted nearly to the end of the 
Cretaceous formation. The great majority of species are known from Europe, where, 
as I have mentioned, they occur in all three mesozoic formations. Only one species 
has previously been found in Spitzbergen (Hulke, 1873, p. 10; Stensio, 1918b, p. 76); 
three species are described from the Triassic of North America (Jordan, 1907, p. 100; 
Wemple, 1906, pp. 71—72) and one from its Cretaceous; finally one species is known 
from the upper Cretaceous of South America (Woodward, 1889 a, p. 297). 
On account of the fragmentary state in which they are preserved the Acrodus 
species have always been and still are, as has already been pointed out, difficult to 
treat from a systematic point of view. Just as in the case of the Hybodus species the 
different authors are very different opinions with regard to the actual limits of species. 
Now-a-days, especially in the case of the Triassic ones, there is, however, a tendency 
to consider, with good reason, that a number of species names proposed by Agassiz 
and several succeeding authors may to a considerable extent be regarded as synonyms. 
From the Spitzbergen Triassic we now have, as the subsequent description will 
show, four species, of which one, A. spitzbergensis Hulke, is, as has been pointed out 
above, already known previously. The relationship between these four and the other 
known ones is of course not yet fully ascertained, but as far as can now be seen, 
1 ) Philippi and Frech (1903, p. 11) also refer Woodnika althausii (Munster) to Acrodus. Although the genus 
Woodnika is undoubtedly closely related to Acrodus, at least at present it seems as if it ought not to be included in the latter. 
Stensio, Triassic Fishes from Spitzbergen. 2 
