442 



The valve of an Australian freshwater shell {Melania nana) adheres to the front 

 pier of the right zygomatic arch, just above the masseteric process, which descends 

 outside the socket of the last molar (m 1) coming into place. The movements attending 

 the growth of the maxilla, whereby the relative position of this process to the hindmost 

 molars, subsequently developed, is changed, have been already noted. 



For fuller illustration of the dental characters of Sthenurus Atlas, figures of portions 

 of the right and left maxillary, each with the two anterior teeth (p 3, d *) of the mature 

 dentition, are given in Plate LXXXVIII. figs. 1-4. They show the low transverse 

 ridges crossing the bottom of the valley between the high outer and low inner wall of 

 the crown, and repeat other characters exemplified in the jaws of the mature animal 

 (Plate LXXXIV. figs. 4-6) by which the genus Sthenurus is distinguished from the 

 genus Protemnodon and from the genus Halmaturus. 



For further exemplification of the two specific representatives of Sthenurus, figures 

 of portions of jaws of a mature Sthenurus Brehus are given in Plate LXXXVIII. figs. 

 5, 6. 7, corresponding with the subjects of Sthenurus Atlas in Plate LXXXIV. Further 

 exemplifications of the larger species are the subjects of the following section. 



§ 16. Sthenurus Brehus (restoration of dentition and skull). — This species was founded 

 on a maxillary portion of cranium with the left molar series, in part mutilated, and with 

 the last two molars of the right side (Plate LXXXVII. figs. 5 & 6) ; also on a fragment 

 of the left maxillary with the premolar and contiguous molar entire (ib. figs. 7, 8, 9) 

 from a younger individual. Both fossils were from Mitchell's Breccia-cave in Wel- 

 lington Valley, New South Wales, and formed the first evidence of this extinct species 

 which came to my hands. 



Since the text and plate illustrative of these fossils were printed off I have been 

 favoured, through the persevering and successful quest of George F. Bennett, Esq., in 

 Queensland, son of my old and esteemed friend Dr. George Bennett, F.L.S., of Sydney, 

 New South Wales, with portions of the skull and lower jaw of older and younger indi- 

 viduals of the same species, from the freshwater drift at Clifton Downs, Queensland. 

 One of these specimens exhibits the entire molar series, left side upper jaw, with that 

 of the right side, less the last molar ; another fossil includes the premaxillaries and 

 upper incisors ; and a third consists of the fore part of the mandible with the lower 

 incisors and with the first three molars of the right side. All three specimens are parts 

 of the same skull. 



A fourth lot consisted of four portions of the upper jaw of a mature but younger 

 individual than the subject of Plate LXXXVII. ; they included the incisors and pre- 

 molars of both sides, and the entire molar series of the right side. 



A fifth specimen consisted of the fore part of the upper jaw of an aged individual 

 with much of the crowns of the incisors worn away, and the smaller ridges on the inner 

 side of the premolar rubbed smoothly down. 



These specimens instructively exemplify the constancy of the maxillary molar cha- 

 racters of the genus and species, as shown in the type specimens, and add those of the 

 mandible, and the characters of both upper and lower incisors. 



