24 
ERIK A : SON STENSIO 
Finally of the teeth belonging to the posterior transversal rows only a few seem to 
be preserved in the material so far known. A small tooth, about 5 mm long and 2 mm 
high (PL 3 , fig. 11), certainly belongs to this category and, to define it more closely, 
probably to the most posterior transversal row of 
all. The crown and root on this tooth are straight. 
The crown is low and has had a sculpture of delicate 
transversal striae. A couple of other incompletely 
preserved teeth, which are characterized by their weak 
curvature both in the vertical and horizontal plane and 
also by their comparatively small size, but which other¬ 
wise closely resemble the teeth of the median trans¬ 
versal rows in sculpture and other respects, may have 
possibly been situated in the transversal row next 
to the most posterior one or in the third one count¬ 
ing from the last-mentioned row (PI. 3 , fig. 7). 
The present material of A. oppenlieimeri has been 
able, as we have seen, to afford us a more certain 
and complete knowledge of the dentition than is usually 
the case in the Triassic Acrodus species. If we assume 
that this species, like certain other of the same genus 
that are known from the Lias, had 8 transverse rows 
of teeth, the dentition in it ought probably to appear 
about as is shown in text fig. 8. It must however be 
expressly mentioned that there is still much unknown and that this figure is only intentended 
to give an idea of the approximate position of the most important types of teeth so 
• far known. 
The teeth of A. oppenlieimeri show the same conditions as to microscopic structure 
as are usual in the genus Acrodus (cf. Jaekel, 1889). 
Dermal denticles. 
As has already been mentioned there occur together with the teeth of A. oppen- 
heimeri a number of dermal denticles, practically all badly preserved. They are not 
conical in shape as in A. nobilis and A. anningiae (Woodward, 1889, p. 284, p. 289), but 
are as shown in text fig. 9. 
* 
Remarks. — The dentition in A. oppenlieimeri is, as we have seen, composed 
partly of rather different teeth. The teeth of the anterior transversal rows possess in 
the comparatively strong development of the principal cone and the sculpture of the 
crown characters that remind us very much of Hybodus. Certain of them, e. g. the one 
figured in PL 3, fig. 2, have also a rather great resemblance to a number of types of 
teeth of A. minimus (cf. especially the tooth figured by Schmid, 1861, Pl. 2, fig. 38 ), 
The teeth of the median transversal rows and to a certain extent those of the 
posterior ones as well in A. oppenlieimeri are, both with regard to their general shape 
Text fig. 8. Acrodus oppenlieimeri n. sp. 
Schematic restoration of the dentition in one 
half of a jaw, as indicated by the teeth be¬ 
longing to specimen P. 10S and the Acrodus 
species from the Lias. 1/2. 
