New Tijpe of Cetacean Tooth. 151 



A higher power (g^in. giving 380 diameters) shows the cementum, 

 where not obscured by the hyphae of the boring fungus, to be fairly 

 homogeneous, excepting near the inner dentinal layer, where it is 

 penetrated by tlie dentinal tubes, which ramble away from their 

 parallel structure in the ivory. The dentinal tubes are crossed by 

 numerous lines of ivory globules and interglobular spaces, probably 

 air-filled. The dentinal tubes are spaced in each optical layer, 



15/x apart. The hyphal tubes of the parasitic fungus have an average 

 diameter of 5//, 



Observations. — In the microscopic structure of the above tooth 

 there is sufficient evidence to show its close relationship to the 

 living sperm whale, Physeter; but the flattened form of the tooth, 

 which is long — elliptical in section, is a very distinct feature, for 

 only in very extreme examples of that genus can one find a tooth 

 having a broadly elliptical outline. The widely separable forms of 

 tooth base and apex in the two genera are very apparent. In 

 Physeter the base is always more or less cylindrical, or even taper- 

 ing, and the point of the tooth, when depressed, is not hollowed 

 and scalprate as in the above described form. 



The heavy, flattened root and moderately deep pulp cavity re- 

 minds one of the tooth of Hoplocetus, but in that genus the crown 

 is separated from the root by a constriction, and the tooth is fusi- 

 form in shape and not wide at the base, and gradually tapering, 

 as in the present form. In reply to a note and sketch of this speci- 

 men, which I sent Dr. C. W. Andrews, F.R.S., of the British 

 Museum, he has kindly remarked that it does not agree with Hoj^- 

 locetus as figured by Gevvais — whose works, by the way, in the 

 Zoologie et Paleontologie Francaises (vol. I. 1848-52, p. 161) and 

 the Osteographie des Cetaces (p. 345), are not in Melbourne. In 

 view of the fact that the cement layer in this tooth extends over 

 the convex surface almost up to the cutting edge of the apex, there 

 could have been little of the crown exposed, and in view of this 

 character the affinities of the tooth appear to lie with modern 

 sperm whales as Physeter. 



A rolled and otherwise abraded cetacean footh figured by E. Ray 

 Lankester in 186T'i from the Red Crag of Suffolk, may have some 

 generic affinity with the present form. It is stout and fusiform, 

 with a compressed crown, which, so far as the rather obscure .sketch 

 shows, is marked with radiating furrows, as in the Table Cape 

 specimen. 



1. Trans. Uoy. Micr. Soc. Lond., vol. xvi., 1867, pp. 63, G4 (fifr. 3). 



