262 
ERIK A:SON STENSIO 
The dentition of the pterygoid consists of robust, densely situated crushing teeth, 
most frequently rather irregular in shape. The masticatory surface on these teeth often 
show facets, probably due to wearing. 
With regard to the dentition on the mixicoronoid («splenial» according to the ear¬ 
lier terminology, cf. p. 244 above), parasphenoid and gill-arches nothing- is known. 
All the teeth have a pulp cavity of rather considerable dimensions and often a 
milky white point, about as in Colobodus. On the blunt teeth this point has generally 
an unsymmetrical position and is marked off as a verruca; on the pointed ones, on the 
other hand, this condition is less distinct. No striation is present contrary to what is 
the case in typical Colobodus teeth. 
The sensory canals of the head. 
The sensory canals of the head are fine and open outwards with numerous short 
tubuli, which seem to be simple. In most cases the outer opening of the tubuli is diffi¬ 
cult to observe and can be easely overlooked, especially on bones on which the sculp¬ 
ture is developed more strongly. It is of course impossible to decide with certainty 
whether the number of sensory organs corresponded to the large number of tubuli, but 
it does not seem probable that this should be the case, as the entrance foramina for 
the nerves and vessels in the sensory canals are fewer than the tubuli (cf. Allis, 1889, 
PI. XLII; Cole, 1898, PI. 22; Herrick, 1899, PI. XVII; 1901, PI. XIV; etc.). 
As far as can be judged, the sensory canals run in the same way as in the Palaeo- 
niscids. They are partly well preserved and it was possible to follow them all through¬ 
out practically their entire extension. For the reasons in favour of the terminology 
used here see my account above (pp. 102—105, 245—246). 
The supraorbital canal ( soc , PI. 34, fig. 1, text figs. 80, 81) of either side has its 
posterior end situated in the parietal and is developed there for a short distance as a 
furrow, i. e. towards its posterior end it passes over into a «head-line of pit organs» 
{ap, PI. 34, fig. 1), which is undoubtedly homologous with the anterior one in Amia (Allis, 
1889, pp. 505—506), Polypterus (Allis, 1900a, p. 445), and Teleosts (Herrik, 1901, p. 222, 
PI. XIV; Allis, 1905). From the parietal the supraorbital canal continues through the 
frontal, where it does not, however, run straight forward but somewhat laterally as well. 
At the anterior end of the frontal it passes over continously, as in the Palaeoniscids, 
into a part of a canal piercing the antorbital. 
This part of canal, which is thus situated laterally of the nasal apertures, conti¬ 
nues anteriorly and enters the rostral, where it anastomoses with the infraorbital canal 
of its side. As I have pointed out above (p. 246), I agree with Allis (1905, p. 491) that 
this part of the canal does not belong to he supraorbital canal, but that we are here 
concerned with the upper anterior end of the suborbital part of the infraorbital canal. 
The anterior end of the supraorbital canal would thus either be absent or else only 
developed as a «pit-line». If a «pit-line» were present, this would have had its course- 
forwards over the frontal in such a way that it reached the nasalo-postrostral, On which 
it would probably have continued for a short way anteriorly. 
There is no anastomosis developed between the posterior parts of the supra- and 
infraorbital canals. 
