2 ARKIV FOR ZOOLOGI. BAND é. X:0 Z. 



ÅS first object for examination a quite young skull with 

 a basal lengtli of 35 cm. was selected in which the posterior 

 teetli still were hidden in the gum and thus certainly not 

 worn. Since the crowns of the teeth had been laid bare it 

 was apparent, as may be seen from the accompanying figures 

 (fig. 1), that not only the four posterior teeth of the lower 

 jaw, but the majority of all the teeth in the upper as well 

 as in the lower jaw were provided with accessory cusps. At 

 least the third from the front as well above as below has such 

 cusps more or less developed, and even in front of that traces 

 of such may be discerned on the teeth. The anterior teeth 

 are more pointed than the posterior which are broader and 

 stronger. All the teeth are compressed, especiall}^ at the apex, 

 their inner side is somewhat flatter than the outer, and the 

 cusps are of ten better visible from the inner side. The whole 

 crown is a little curved inward with the apex, as True has 

 remarked. In most cases only two accessory cusps are devel- 

 oped, one in front, and the other behind the main cusp. In 

 the posterior teeth, however, the cusps are more sharply 

 defined, and in some their number is increased in such a way 

 that the teeth remind of those of certain Squalodontidce. The 

 figures may prove this and make a further description un- 

 necessary. In reality, however, a fine crenulation, which 

 hardly can be reproduced makes this likeness still more strik- 

 ing in some cases. The crown of the teeth is quite small 

 measuring in the upper jaw basally where it is broadest 

 between 2 and not quite 3 millimeters in diameter. The 

 foremost teeth attain however hardly that width. As the figures 

 prove, the width of the teeth increase in a backward direction. 

 The, height of the crown is, as a rule, about 4 mm., some- 

 times a little more or less. The crowns of the teeth of the 

 lower jaw are still smaller their basal diameter, as a rule, 

 being about 2 mm., and their length about 3 mm., or very 

 little more. Compared with the size of the animal the crowns 

 of the teeth must be regarded as very small and can with 

 full right be termed rudimentary. At the base of the crown 

 the root of the teeth is abruptly thickened, forming a collar, 

 but from that thickening the root retains its size or even 

 increases so that it forms a long and stout cylinder fully 

 open basally. The dimensions of the roots in this stage are 



