40 KECOEDS OF THE AUSTRALIAN MUSEUM. 



Assuming this to be correct, one of the faces of the trihedral 

 process, the dorsal, is flattened, or in the slightest degree convex ; 

 the under, or ventrolateral, being faintly concave, and the 

 posterior flattened and to some extent truncate. The apex is 

 sharp, acuter than any of the processes flgured by Sir R. Owen.* 

 but less generally cornute than the supra-temporal cores b of 

 the head.f 



The second specimen only differs materially from the first in 

 the antero-apical line losing much of its ridge-like character, 

 and becoming obtusely rounded. Owing to the more extensive 

 preservation of this part of the process, and the disintegration of 

 the posterior lower portion, this horii-corB presents the appearance 

 of a greater obli(}uity than the other. The length of the antero- 

 apical obtuse ridges is four inches; the aiitero-posterior diameter 

 is four and a half inches ; the transve I'^e diameter three inches ; 

 and the height two and three-(iuarter inches. The lateral and 

 posterior faces are flattened. The surface of both cores is pitted 

 and veined by ueuro-vascular markings. 



If, in the first place, it be admitted that these are osseous cores 

 for the support of dermal appendages, their interpretation does 

 not seem surrounded with much difficulty. We are not acquainted 

 with any Australian extinct animal, other than Meiolania, possess- 

 ing such exoskeletal outgrowths: and as we know only the skull, 

 part of the tail-sheath, and a few individual bones of this genus, 

 it is but logical to compare these bony processes with those of 

 either one or other of the former. 



The horn-cores of the skull in Meiolania are either depressed 

 mammillary (the supra-parietal and other smaller pairs), or acutely 

 conical and cornute (the supra-temporal pair). Those of the tail- 

 sheath, on the other hand, arranged in four parallel rows, two 

 dorsal and two lateral, are " massive conical processes, like the 

 horn-cores of the skull, but of larger size, being broader and 

 thicker in proportion to their length, and rather more robust at 

 the apex;"| the upper or dorsal pair being the largest and longest. 

 The appearance of our fossils would indicate that they are from 

 the rings of a tail-sheath, although on comparison with a good 

 plaster reproduction of M. Owenii, they are seen to be more 

 strictly trihedral, and their apices naore regularly conical and 

 sharper than in the former. The difference in shape may perhaps 

 be more apparent than real, and arise in a great measure from 

 their detached condition and imperfect peripheries ; although at 

 present their bases are wider in proportion to the height than in 



* Phil. Trans., clxxi., t. 37 ; Ibid, clxxii, t. 65. 



fPhil. Trans., clxxi., t. 37, f. 1, 6' 



X Phil. Trans., clxxii., p. 547. 



