34 
ERIK A : SON STENSIO 
It is also possible that the teeth from the upper Tiriassic in North California, 
described by Bryant under the name of Strophodus shastensis (1914), belong to Palaeobates. 
At any rate these teeth show a rather considerable resemblance to Palaeobates teeth in 
their general shape and the same seems to be true of their sculpture. In this case the 
microscopic structure would certainly show quite distinctly if we were concerned with 
teeth of Palaeobates or Strophodus, but this is still unknown. 
The material from Spitzbergen now makes it possible to give a somewhat more 
complete definition- of the genus Palaeobates than previously. The characters so far 
known can be summarized as follows: Mandible short and high with comparatively 
few, probably only five or six transversal rows of teeth; possibly an unpaired symphyseal 
row is also present. The third and fourth transversal rows, counting from behind, each 
consists of long, large teeth, the rows that follow anteriorly and posteriorly consist of 
smaller teeth, the most posterior row having even very small teeth. The anterior teeth 
have a more strongly arched crown than those following posteriorly. The dentition in 
the palatoquadrate is not known in detail, but it possibly differs somewhat from that 
of the lower jaw. All the teeth, both in the palatoquadrate and the mandible, have a 
flattened, long and narrow crown without lateral cones, but sometimes with a principal 
cone. A longitudinal crista is often present, but may also be absent. The sculpture of 
the crown consists of fine, very much ramified striae, in certain species anastomosed 
with each other and forming a network. The crown has a rather thin layer of enamel, 
apart from which it is entirely formed of ortho-dentine; the root consists of trabecular- 
dentine. There is often the remains of a pulp cavity between the root and the crown. 
The Spitzbergen material confirms the view that we have in Palaeobates a genus 
differing distinctly from all other known Selachian genera. It is also clear that Palaeobates 
most closely resembles Polyacrodus with regard to the microscopic structure of the 
teeth, while on the other hand, to judge from the general shape and arrangement of 
the teeth, it seems to occupy an intermediate position between Acrodus and Aster acanthus. 
If a family Hybodontidae is accepted with the definition of Koken and Schlosser in the 
later editions of Zittel’s «Grundziige der Palaontologie», there is no doubt that 
Palaeobates ought to be included in this family. 
Palaeobates polaris n. sp. 
(PI. 3 , figs. 12—18.) 
This species is represented by two specimens (P. ioy and P. 108). On both there 
are remains of teeth and dermal denticles. One (P. ioy) has also a number of parts of 
the visceral skeleton preserved. 
Visceral skeleton. 
The visceral skeleton is calcified in the usual way in its peripheral layers. The 
calcified layer seems to be about o - 5—1 mm thick. 
Only small portions of the palatoquadrates are preserved. The right mandibula 
is fragmentary, the left, on the other hand, is almost perfect, as only its postero-dorsal 
corner is absent (text fig. 14; PI. 3 , figs. 16 a,- b). 
