THE SOUTHERN BOTTLENOSED WHALE 27 



The greatest diameter is just a little distance above the lower edge of the tooth, which has this 

 indication of incipient closing of the pulp cavity. The tip of each tooth, an unworn crown of about 

 8 mm. length, projects from a thin investing coat of cement. 



The South Australian specimen has much more massive, fusiform teeth. Their length is comparable 

 to that of the Discovery specimen — 57 and 59 mm. — but the greatest diameter is double. Apart from 

 the difference in the pulp cavity (the root is entirely closed in the South Australian specimen) which 

 is due to age, it is considered that the dissimilarity is associated with sex, and that in this as in other 

 ziphoid whales the teeth of the male are large, massive and projecting above the gum, whilst those 

 of the female are more slender, and, since the crowns are unworn, presumably concealed by the gum. 



Fig. 4. Teeth of H. planifrons. 

 Upper pair, 9, Discovery 

 specimen ; lower pair, S, South 

 Australian specimen. ( x \.) 



Fig. 5. Anterior view of atlas. 



(xi) 



VESTIGIAL TEETH IN THE UPPER JAW 



When the Discovery specimen was received the skin and dried flesh on the ventral surface of the 

 rostrum were still attached, and on each side of the upper jaw was a row of teeth commencing at 

 about 24 cm. from the jaw tip and extending along the jaw about 16 cm. The teeth were spaced roughly 

 equidistantly about 8 mm. from each other. All of the teeth were not in situ ; some had either been 

 absorbed or had dropped out, but evidence of their existence was indicated by the fibrous follicles 

 in which they had rested. It was estimated that each row consisted of twenty teeth, but the difficulty 

 of dissection made exact computation impossible. Sixteen teeth were recovered on each side ; most of 

 them projected 2-3 mm. from the dried gum, but whether this post-mortem conspicuousness existed 

 in the living animal is doubtful. Their shape is fusiform and they are slightly to moderately curved. 

 A basal portion consisting of cement envelopes the dentine of the crown to a greater or lesser extent, 

 in some the junction between cement and dentine being clearly defined. The root portion of some of 

 the teeth is drawn out into a needle-like extension. This is considered to be due to absorption in 

 process, and in the shorter teeth, in which the extension has disappeared, it is presumed that the 

 process has gone still further. The length of the teeth ranges from 4 to 14 mm. with diameter up 

 to 2 mm. 



VERTEBRAE (Figs. 5, 6) 



Vertebral formula. Cervical 7, dorsal 8, lumbar 11, caudal 17 + . 



Cervical vertebrae. The Discovery specimen, like the South Australian and H. rostratus, has all 

 seven centra fused together. The posterior epiphysis of the seventh is still distinct. In correspondence 

 with the superior size of the occipital condyles in H. rostratus the anterior articular surface of the 



