TRIASSIC FISHES FROM SPITZBERGEN 
On the root one can distinguish a medial, a lateral and a basal surface. The last- 
mentioned surface is divided lengthways into two fields (text figs, i A, B), a medial 
and wider one, above which the axis of height of the principal cone is situated verti¬ 
cally, and a lateral one,, which forms an angle of about 45 0 with the former. The lateral 
surface is fairly low and a little concave from the distal to the basal border (text 
figs. 1 A, B). The medial surface on the contrary is convex in the same direction and 
is developed especially at the ends in such a way that we are quite justified in speaking 
of two fields there, a medial and a dorsal one (text fig. 1 B).. . 
With regard to the microscopical structure the two teeth now described do not 
differ in any respect from other typical ones (cf. Jaekel, 1889; Koken, 1907) 1 ). On the 
root numerous Haversian canals with rounded pores open in the usual way. 
Remarks. — H. rapax undoubtedly resembles the type of teeth that was de¬ 
scribed and figured by Agassiz (1843, vol. 3 , PI. 24, figs. 19, 20, 21, 23 ), Plieninger (1844, 
Tafel XII, figs. 54, 56) and Quenstedt (1852, Tafel i 3 , figs. 3 o, 3 i) and others under the 
name of Hybodus longiconus, as it differs from that type only by its larger size and 
the extension of the ornament on the lateral side of the crown. With the type of teeth 
for which Jaekel 1889 has chosen the name Hybodus longiconus, on the other hand, the 
species in question from Spitzbergen does not agree so well. 
Hybodus rapax in several respects also seems nearly related to the new species 
Hybodus sasseniensis described below, and we must therefore take into account the 
possibility that in future with more complete material it may perhaps show itself to be 
identical with the latter. 
Geological occurrence and locality. — A bone-bed about 33 m above the 
fish horizon, Mt Viking. 
Hybodus sasseniensis n. sp. 
(PI. 1, figs. 3—10.) 
Synonym: 1918. Hybodus sp. Stensio e. a : son, Norsk Geol. Tidskrift, Bd. V, p. 76. 
I have established the species H. sasseniensis for six detached teeth (P. 3g a — f), 
five of which (a — e) are in a comparatively complete state of preservation. To this 
species may be added with a fairly great degree of probability three more teeth (P.38, 
P. 40 , P. 633) and, at least provisionally, the tooth from Horn Sound previously 
described by me (Stensio, 1918 b) and another tooth, mentioned at the same time, from 
Middle Hook in the Ice Fjord, which is the property of Prof. Dr. W. Salomon in 
Heidelberg. — The tooth from Horn Sound belongs to the Palaeontological Collection 
of the University of Christiania. 
The largest ( P. 3gb) of the six teeth given as typical of the species in question 
is about 12 mm long, the smallest (P. 3gf) about 6 mm. The height can only be 
l ) It may be mentioned here that Jaekel 1889 and several other palaeontologists have used the term 
vaso-dentine for the tissue we now callosteo-dentine (Tomes, 1914, p. 102) or trabecular-dentine (Rose, 1898, p. 42) 
in the teeth of Selachians. 
