LÖNNBERG, THE DENTITION OF DELPHIXAPTERUS LEUCAS. 7 



versal diameter usually is a little shorter; but in the lower 

 jaw of the same skull they are lateraliy compressed so that 

 to a diameter of 7^/2, 7 or 6 mm. in the direction of the jaw, 

 corresponds a transversal diameter of resp. 5, 4V2 and 4 mm. 

 It lies near at hand to put this transversal compression 

 in connection Avith the fusion of two roots which has been 

 proved to have taken place among the Squalodons. This 

 came to my mind the more readily as the pulpcavity of a 

 tooth which I examined proved to be divided at the apical 

 end into two pits, which might indicate the fusion of two 

 roots. When the examination was extended to a greater 

 number of teeth of this and other skulls this hypothese was 

 not, however, confirmed. It is true that there was found in 

 some teeth a small conical plug protruding into the apical 

 end of the pulpcavity, but it had not the appearance of a 

 sep tum, and it could not be 

 said to indicate a former divi- 

 sion in two pulps. In most 

 cases the pulp cavity ended in 

 a simple conical pit. Exteriorly 

 the roots in this stage are more 

 or less flattened, especially on 

 the inner side and there is not 

 seldom a quite shallow groove 



along the middle of the tooth Fig. 2. A tooth from the lower 



as Well on the OUter as on the ^^ ?f a White whale (basicranial 



length about 49 cm.) with the upper 

 inner side. If SUCh a tooth is part transversally cut off to show 

 CUt in sections transversal to ^he central fissme in the dentine 



. and its situation. 



the tooth itseli there is often 



found a fissure which is directed transversally in relation to 

 the jaw and which extends across or nearly across the central 

 cylinder of dentine (fig. 2). The common occurrence of this 

 fissure in the dentine is proved by the fact that a great 

 number of teeth, especially in the lower jaw, are cracked^ 

 longitudinally along a plane transversal to the animal, and 

 that this crack is coincident with the above mentioned fissure 

 in the dentine in all cases when a section has been made. 

 This fissure in the dentine looks hke a remnant of the pulp- 



4 ^ 



^ In consequence of the drying in the museum. This cracking affects 

 as a rule mostly middle sized teeth. The cjuite large ones are better pro- 

 tected against it by a thicker coat of cement (conf. the description below). 



