379 



the palatine (20"), and develops a short compressed "hamular" process ( 24') slightly 

 bent outward. 



The petrosal (ib. fig. 3, 10) has two free surfaces — the "cranial" and "basilar." 

 The former is the most extensive, is bifurcate anteriorly and impressed near its hind 

 part by a deep cerebellar pit, below and a little in advance of which is the " meatus 

 auditorius internus;" a sharp ridge overhangs the cerebellar or appendicular pit. The 

 exposed basilar surface is small and narrow, pointed anteriorly, grooved externally 

 for a venous canal, and, in most Kangaroos, crossed by a slender bar of the exoccipital 

 uniting with the paroccipital process of the alisphenoid. The lacrymal has a small 

 "facial" (ib. fig. 1, 73') and a large "orbital" plate (73); the angle between the two 

 shows two foramina with an intervening tubercle ; and in some species of Kangaroo there 

 is a second tubercle above the upper foramen. These lacrymal foramina (ib. fig. 2, I, I') 

 are rather ectorbital than entorbital ; both lead to a canal descending and bending 

 forward to terminate in the nasal meatus. 



The angle of the lower jaw (ib. fig. 1, a) is tumid, strongly inflected and upbent into 

 a ridge bounding a wide and deep concavity, indicated by as strong a convexity (k) ex- 

 ternally. The fore part of the cavity communicates with the external crotaphyte fossa 

 (f) by a perforation, in front of which is the entry of the dental canal. The symphysis 

 is long, narrow, and usually rather loose, permitting movements of the rami on each 

 other 1 . There are no subsymphysial foramina as in Phascolomys. The vertical extent 

 of the ramus increases from behind the last molar (m 3) to the antepenultimate one 

 (m 1) ; it suddenly decreases in front of the molar series, and is continued forward 

 along an extensive diasteme (I, I), chiefly devoted to the support of the long pro- 

 cumbent incisor {%'). The external orifice of the dental canal (v) is a little in advance 

 of the molar series. 



The skull which forms the subject of PI. LXVI. is from a male Rufous Walleroo, 

 which measured 8 feet 2 inches from the nose to the extremity of the tail. This 

 animal had the last molar in place and use, and still retained, though much worn down 

 and probably soon to be shed, the tooth answering to the last of the deciduous series in 

 Diphyodont Mammals (ib. fig. 6, d 4); the phase of dentition answers to that marked F 

 in my article "Odontology," in the ' Encylopaedia Britannica' (vol. xvi. p. 484) — the 

 teeth, according to the symbols there adopted and explained, being d 4, m 1, m 2, m 3 ; 

 consequently three of the molar series, viz. p 3, d 3, and d 2, had been shed. 



1 " The Mus maritimus, or African Eat, has the singular property of separating at pleasure to a considerable 

 distance the two front teeth of the lower jaw, which are not less than an inch and a quarter long. That 

 elegant and extraordinary creature, the Kangaroo, which, from the increase that has lately taken place in his 

 Majesty's Gardens at Kew, we may soon hope to see naturalized in our own country, is possessed of a similar 

 faculty." — Mason Good, The Book of Nature, 8vo, 1826, vol. i. p. 285. This power of divaricating the lower 

 incisors, or rather their sockets, through laxity of the ligamentous symphysial joint, has since been noticed by 

 Waterhouse (Nat. Hist, of the Mammalia, 8vo, 1845, vol. i. p. 52), and by myself and others. 



