222 
ERIK A : SON STENSIO 
scales are all somewhat broader than high and have the anterior, covered area fairly 
wide, although scarcely so wide as in the typical Boreosomus species described above. 
The sculpture consists partly of striae, partly of tubercles. The striae, which pass off 
obliquely backwards and downwards, are long with sharp backs, and often wide; they are 
also situated close together. Those that are situated nearest to the lower margin on 
each scale may not infrequently have their anterior ends bent upwards parallel to the 
anterior margin, but they never run any long distance in this way, as is the case in 
B. arcticus. All the striae have the very fine folds previously described by me in Boreo¬ 
somus sp. and Boreosomus reuterskioldi. 
The tubercles on each scale are situated in front of the anterior ends, of the striae, 
where they are arranged in a couple of rows parallel to the anterior margin of the 
scale. The tubercles themselves are somewhat lengthened in a dorsi-ventral direction. 
The sculpture of the scales obtains through the arrangement of the tubercles a feature 
that recalls Boreosomus arcticus to some extent. 
If we now turn to the detached scales (PL 26, fig. 3 ; PI. 35, fig. 4) we are able to 
distinguish different types according to the position they have occupied. We find some 
that are higher than wide, having evidently been situated rather close behind the 
shoulder girdle, some in which the height is slightly less than the width, having 
belonged to the middle part of the lateral sides of the abdominal region, and finally 
those in which the width is considerably greater than the height. These last-mentioned 
scales are probably from the ventral side and the back. 
These scales are closely related in all respects to those just described above in 
specimen P. 877, but differ from these by having the vertical rows of tubercles in front 
of the striae in most cases more numerous, usually three and sometimes even four or five. 
Remarks. -— The scales described here show such agreement in their characters 
in several sespects that I consider myself able provisionally to group them under one 
species name. They resemble somewhat those in Boreosomus arcticus. 
Finally it must be pointed out that the generic determination of these scales must 
be looked upon as rather uncertain. 
Geological occurence and localities. — Specimen P. 877 comes from the 
fish horizon at Mt Bertil. 
The detached scales occur in the bone-bed of the lower Saurian horizon, and in 
bone-beds between this and the fish horizon. In the bone-bed of the lower Saurian horizon 
they sometimes appear in such great numbers that they really form the rock. The 
localities of the finds are as follows: The mountain between De Geer Valley and Flower 
Valley (Corrie Down) on the south side of Sassen Bay, Mt Marmier and Mt Viking. 
Genus Acrorhabdus n. g. 
As far as is known up to the present, the new genus that I call Acrorhabdus is 
characterized by the following features: Small to medium fusiform fishes. The primor¬ 
dial neurocranium like the primordial visceral skeleton strongly ossified. The posterior 
part of the entopterygoid is, at least in certain species, represented by a number of 
