407 



of the two anterior ones, shows a modification of those of the three following (m i, m 2. 

 m 3) which I now know to be a variety, although not such as to induce me to refer the 

 fossil to another species. The mid link (fig. 3, r) as it passes forward from the hind to 

 the front lobe expands and divides ; the more direct or normal continuation, after reaching 

 the front lobe, bends to terminate or be continued into the inner border of that lobe ; 

 the other lower and shorter division turns outward to be lost upon the lower part of 

 the outer half of the hind surface of the front lobe. 



This character I briefly expressed as " a more complex form of the longitudinal ridge 

 connecting the two principal transverse eminences : ' than in Macropus major or Macro- 

 pus laniger, in my 'Catalogue of the Fossil Mammals* in the Museum of the Royal 

 College of Surgeons ' ; at the date of which work this specimen was the sole evidence of 

 the upper jaw and teeth which appeared to me to be referrible to Macropus Titan. 



Besides the structure of the grinding-surface of the molars above defined, those in fig. 3, 

 Plate LXXX1II., are arranged with a curve rather more marked than in the subject 

 of fig. 11, Plate LXXX1I. ; but as the teeth here are less straight than those in the 

 subject of fig. 8, Plate LXXXL, this seems to be but a ground of variety. The relative 

 position of the zygomatic pier in figs. 2 & 3, Plate LXXXIIL, may relate to the recent 

 movement of m 3 into its working position : the untouched lobes of this tooth are longer 

 and sharper than usual; yet the general concordance with the molar characteristics 

 of Macropus Titan lead me still to refer the specimen No. 1510 to that species. 



The modification of the mid link seems a small matter, but is not so in the actual 

 phase of zoology. Evolutionally speaking, this variety may be viewed as either a rem- 

 nant or a dawn of a complex condition of the part which will be described in 

 subjects of a subsequent section. 



Of the mandibular dentition of Macropus Titan an early stage is exemplified in the 

 fragment of lower jaw f rom the Breccia-cave of Wellington Valley on which the species 

 was founded f. 



I have given an improved figure of the outer side of this specimen, with the pre- 

 molar exposed in the primitive alveolus, in Plate LXXXI1. fig. 18, and have added a view 

 of the grinding-surface of the two mutilated molars in situ (ib. fig. 17). This portion 

 of (right) mandible of Macropus Titan includes the hind part of the first molar (d 4) and 

 a larger proportion of the succeeding molar (in 1). The anterior lobe of this tooth is 

 entire ; the hind part of the posterior lobe is broken away. 



The anterior talon or " prebasal ridge " of m 1 has almost the character of a lobe ; it is 

 united to the anterior normal transverse lobe by a well-developed fore link, commencing 



* 4to, 1845, p. 324, No. 1510. 



t Three Expeditions, 8vo, 1838, by Sir Thomas L. Mitchell, C.B., vol. ii. p. 359, pi. xxix. fig. 3. This 

 specimen, with other fossils from the Wellington Valley cavern, submitted by its discoverer to me, were pre- 

 sented to the Geological Society of London, to the President and Council of which I am indebted for the 

 opportunity of reexamining and figuring this collection, which initiated our knowledge of the fossil Mammals 

 of Australia. 



41* 



