8 • ERIK A : SON STENSIO 
type. Other clear differentiating - characters are difficult to state, but, in spite of that it 
seems fairly certain, from what I have been able to make out by direct comparisons, 
that the Spitzbergen types described here represent a new and independent species for 
which I have suggested the species name sasseniensis after the place of discovery of the 
type-teeth, Sassen Valley. 
Geological occurrence and localities. — The six typical teeth (P. 3 g;a — -f) 
all are obtained from the bone-bed, found 33 m above the fish horizon, Mt. Viking. 
From the same locality and horizon the teeth P. 38 , P. 40 and P. 633 also originate. Of 
the two others, about whose determination I am not quite certain, one, as has been 
mentioned, was found at Horn Sound, the other at the Ice Fjord in a bone-bed which 
was discovered by Salomon in the sandstone series below the fish horizon during 
the excursion of the Geological Congress to Spitzbergen in 1910 (Stolley, 1911, p. 1x5). 
Hybodus microdus n. sp. 
The available material of this species consists of two crowns of teeth (P. 53, P. 54). 
Both teeth have been very small. The length of the crowns is only 1-5 mm and 
the height about 1 mm. 
The crowns are. somewhat bent, as shown in text figs. 3 A and B. Their principal 
cone is strikingly powerful, with a broad base and a sharply pointed distal end, and 
seems to be fairly flattened from both the medial and the lateral 
side. In addition it is somewhat inclined both in posterior and 
medial direction and has a sharp anterior and posterior edge. On 
the tooth P. 5 3 lateral cones seem to be absent in front of the 
principal one, but this fact may be due to the state of preser¬ 
vation, which in this part does not seem to be quite perfect. Be¬ 
hind the principal cone two lateral cones are found on the same tooth, and this is the 
case on the other tooth both behind and in front of the principal cone. 
The tooth P. 54 in quite smooth, at least on the lateral surface. On the other 
tooth some long striae can be observed on the corresponding surface; they reach almots 
to the distal end of the principal cone, Neither tooth has the medial side accessible for 
a close investigation. * * 
* 
Remarks. — H. microdus resembles in several respects both H. minor Agassiz 
and H. apicalis Agassiz (cf. Agassiz, 1843, vol. Ill, p. i 83 , PI. 23 , figs. 21—24; p. 195, 
PI. 23 , figs. 16—20), but seems, however, to be related most closely to tjie latter. It is 
characterized especially by the smallness and slight ornamentation of the teeth. 
Geological occurrence and locality. — Both teeth were found at Mt. Viking, 
in the bone-bed about 33 m above the fish horizon. 
Genus Acrodus Agassiz. 
Synonyms: See Woodward, A. S., The Wealden and Purbeck Fishes, etc., Palaeontogr. Soc. Vol. 69, p.14. 
The genus Acrodus was established by Agassiz, i 838 (vol. Ill, p. i 3 g). Many investigators 
have since helped to extend our knowledge of this genus and among them we may 
Text fig. 3. 
Hybodus microdus n. sp. 
Teeth A, after P. 5s; 4/1. 
B, after P. 54; 6/1. 
