542 



PEOFESSOE OWEN ON THE EOSSIL MAMMALS OF AUSTEALIA. 



In Diprotodon the length of the third cervical centrum is 1 inch 10 lines, the breadth 

 of its hind articular surface is 4 inches 3 lines, the height of the vertebra is 8 inches. 

 The centrum is without hypapophysis, the vertical extent of the hind surface (Plate 

 XLIV, fig. 4, (?) is 2 inches 9 lines ; the two extremes of the transverse ellipse are almost 

 angular. The base of the parapophysis (ib. and cut, fig. 5, p) extends from near this 

 angle forward for 1| inch along the side of the centrum. The upper surface of the 

 centrum shows a large medial venous orifice. Both margins of the rising neurapophyses 

 are deeply notched for the " conjugational foramina," and send off a small diapophysis 

 (ib. d) to circumscribe above the vertebrarterial canal. The neural spine (ib. ns), 4 inches 

 in height from the roof of the neural canal (ib. n), is compressed from before back- 

 ward, simple, obtusely rounded at the end, strengthened by a low medial ridge, both 

 before and behind, along its basal half. There is no such development of neural spine 

 in the third cervical of Proboscidians ; in the larger herbivorous Marsupials it is as con- 

 spicuous as in Diprotodon, but with altered shape ; that in the Wombat most resembling 

 the one in Diprotodm, but being relatively lower. 



The fourth cervical (Cut, fig. 5, c 4) much resembles the third ; but, as in the 

 Kangaroo, has a shorter spine, resembling, however, in shape that of the third, being 

 compressed from before backward instead of from side to side as in Macropus. The slight 

 increase of size is in breadth, chiefly of the centrum, not in length or height. The neural 

 canal is wider and a little higher ; more space is made for the myelon as it traverses the 

 more flexible part of the neck. The large venous foramina and vertical canal are repeated 

 on the upper part of the centrum ; the corresponding pair of foramina now also blend 

 into a common fossa, as in the Wombat. 



In the fifth cervical (Cut, fig. 5, c 5) the neural spine gains in antero-posterior and 

 loses in transverse thickness ; the vertical ridges are J'ig- 5. 



stronger, especially the one behind ; it appears to 

 have been shorter than in the fourth vertebra*. 

 The centrum and neural canal have increased, chiefly 

 transversely ; there is very little increase of length. 

 The parapophysis has gained in vertical extent. 



In the series of mutilated vertebrae belonging to 

 Mr. BoYiys specimen of Diprotodon are two dorsals 

 (Plate XLIV. figs. 5-8). They show the impres- 

 sions for the free articulation of the ribs both before 

 and behind (ib. figs. Q8c7 ,pl,pl'), and arc remarkable 

 for the retention of the short proportion of the cervicals, and for the terminal bifur- 

 cation of the antero-posteriorly compressed spine (ib. figs. 5 & 8, ns). They are not con- 

 secutive vertebra?, but were not far from one another in the anterior part of the dorsal 

 series. 



• It in HO in the sketch sent me by Sir Thomas Mitcheli, from Sydney (Cut, fig. 5) ; but, amongst the 

 damages to the specimens in their passage to London, the summit of this spine has been knocked off. 



A c4, c5 

 Second to fifth cervical vertehrae, one-sixth 

 nat. size; Diprotodon. 



