ERIK A : SON' STENSIO 
■The dimensions of these in their present state of preservation are as follows: 
P. 41 a. P. 41 b. 
Height (with the principal cone partly preserved) . . 32 mm 3 o mm 
Length.23 „ 35 „ 
The greatest height of the root.n ,, 11 „ 
The breadth of the root at the middle.— „ 15 „ ' 
The breadth of the crown at the middle.10 „ 10 „ 
It is certain, however, that both the height and the length have been considerably 
greater than is indicated by the above measurements. The real height may be estimated at 
about 35 mm and the length at least 40 mm (cf. Pl. 1, figs. 1 a, b). It is thus evident that 
these teeth are larger and more powerful than any other Hybodus 
teeth so far found. 
The crown on both teeth is bent basally in such a way that 
its lower margin is strongly concave, as is shown by PI. 1, figs. 1, 2. 
The greatest breadth and height of the crown are at its middle 
part and decrease from there continually towards the ends. The 
lateral cones are quite absent. The principal cone, on the other 
hand, is strong and seems to have occupied a nearly symmetrical 
position. It is, however, not vertical but inclined somewhat back¬ 
wards and at the same time also medially. It is flattened in the 
latero-medial direction and a horizontal section through it con¬ 
sequently becomes ellipsoidal in shape. A sharp longitudinal keel 
is developed along both its anterior and posterior edges, but to 
judge from specimen P.41CI, this keel extends only on the posterior side right out to the 
point. On the anterior side it fairly soon becomes more delicate and finally disappeares 
altogether. From the principal cone the keel continues out over the rest of the crown 
to each of its ends. 
The sculpture of the crown consists of numerous vertically running striae, all of 
which issue from the basal margin. These striae are coarser on the medial surface of 
the crown than on the lateral one and, as a rule, longer too and have a distinctly 
thickened proximal end. On the principal cone they extend on the medial surface 
up to about the middle, while dorsally of this the sculpture is quite lacking. In front of and 
behind the principal cone several of the striae of the medial surface reach the longitudinal 
keel. On the lateral surface, on the other hand, the striae are short throughout the 
whole length of the crown and limited to its basal parts; the rest of this side is smooth. 
The other characteristic features of the sculpture are clearly shown in PI. 1 , figs. 1, 2. 
The root is high and powerfully developed. Seen from the lateral or medial side 
it appears, like the crown, to be bent so that its basal border is concave and its distal 
border convex to a corresponding extent. The curvature of the root seems, however, 
to be somewhat weaker than that of the crown. The root has its greatest height at its 
middle part; toward the ends it gets gradually lower. It is considerably wider than 
the crown, and, as the latter is not situated right above it, but more above its lateral 
part, the medial part appears as a powerful torus on the medial side (text figs. 1 A, B). 
Text fig. 1. 
Hybodus rapax n. sp. 
A). Transverse section through 
the tooth P. 41 a. i/i. B). Section 
through a lateral part of the 
tooth. P. 41 b. 1/1. The lateral 
side of the teeth in the two 
figures is situated to the left. 
