462 



links arc well defined. Deep clefts on the back of the hind lobe mark out the vertical 

 ridges of enamel, of which one is shown at g, fig. 2. The base of the coronoid process 

 (tig. 1, </) advances forward a little beyond m 3. 



The characters of the lower molars of Procoptodon Goliah are further exemplified in 

 a smaller fragment of a large, apparently male, animal, with the last two molars showing 

 a greater degree of wear. This specimen (Plate XCV. figs. 3 & 4, Plate XCTV. 

 fig. 8), now in the Museum of Natural History of Sydney, New South Wales, has been 

 made known to me by a good plaster cast. The penultimate molar (m 2) is slightly 

 worn, the last (m s) in a less degree ; but both had been in use and indicate a full-grown 

 though not old individual. 



The prebasal ridge (ib. ib. fig. S,f), commencing externally at the outer and fore 

 part of the base of the front lobe, rapidly rises as it curves inward, and extends as 

 a thick ridge three lines in advance of the front lobe, rising nearly to its level, and 

 assuming more of the character of an accessory lobe than a mere basal ridge or deve- 

 loped portion of the " cingulum." Its lobular appearance is strengthened by the well- 

 developed link (6 1 ) which connects its outer angle with the fore part of the front lobe 

 (a) near its swollen end. The accessory ridge (n), internal to the link, is well marked, 

 but subsides before reaching the prebasal ridge. This sinks more gradually and with 

 less loss of thickness to the inner and fore part of the base of the front lobe than at its 

 outer end or beginning. The anterior surface of this lobe is broken by minor and less 

 regular ridges and grooves of enamel. The mid link (r) has the same relative position 

 to the transverse eminences it connects as has the fore link ; the inner accessory ridge 

 (0) subsides in the valley; smaller subsidiary ridges and grooves accentuate and multiply 

 the hard enamel-constituent of the grinding-surface of the lower molars, as in those of 

 the upper jaw. 



The last molar (m 3), with a very slight decrease of breadth of the hind lobe, repeats 

 the characters of the preceding tooth ; in both, the hind surface (Plate XCIV. fig. 10) 

 is impressed with a pair of narrow conical excavations, with apices not reaching to the 

 basal beginning of the crown ; these impressions define or leave three ridges (A), not 

 extending back beyond the smooth basal part of the tooth, but which, when worn down 

 to near that part, give a strongly undulating course to the enamelled summit of the hind 

 lobe of the molar. 



The most complete example of a lower jaw of Procoptodon is that which was pre- 

 sented to the Museum of the Royal College of Surgeons of England in the year 1853, 

 by Dr. Faldek, with a note of its discovery in the freshwater or drift beds of Darling 

 Downs, Queensland, " at a depth of 40 feet from the surface of the soil." 



Each ramus of the jaw is preserved as far as the base of the ascending branch ; 

 a small portion of the alveoli of the two incisors, with the corresponding part of the 

 diastemal ridges, has been broken away ; the lower border of the right ramus has like- 

 wise suffered. But the most instructive element in the jaw, viz. the molar series, is 

 almost entire in both rami (Plate XCII. fig. 1). 



