AND A DENTAL NOTATION. 
485 
scribed ; bat although scarcely half the grinding surface of the last molar, m 3, has 
come into use, all the prernolars in advance of the last, p 4, have been shed, Plate 
XXXIV. fig. 8. 
In the specimen of Pfiac. jPlliani, of which the grinding surface of the teeth is 
figured in Plate XXXIV. figs. 6 and 7 of the present memoir, although the major part 
of the last large grinder is in use, the penultimate premolar {p 3) is retained as well 
as the last {p 4). The molar series here shows 5 — .5 in the upper jaw and 4 — 4 in the 
lower jaw; their homologies are indicated by the symbols attached. By reason of 
the precocious development of m\, we now find it quite worn down to the fangs ; and 
in the lower jaw (fig. 7 ) it is wedged between pA and m 2 into a space which is two- 
thirds less than the antero-posterior extent of the crown of the same tooth shown in 
the younger specimen (Plate XXXIII. fig. 2 ). The reduction of size of m 1 is however 
quite intelligible by observing the much-constricted neck from which the long fangs 
are continued in that specimen (see m 1 , fig. 1 ). 
The figures of the grinding surface (figs. 6 and 7) suffice for the characteristic 
forms of the grinding-teeth now in use. 
The specimen of PJiac. Pliant (No. 773. Mus. Coll. Chir.) shows the last remnant 
of m 1 wedged into the diminished interspace between jo 4 and m2, and the corre- 
sponding interspace in the lower jaw, from which such remnant of the first true 
molar has been shed. 
The skull of an older Phac. ^liani (No. 772) shows the displacement of the first 
4 4 
true molar in both jaws and the reduction of the molar series to 333 ; the teeth 
being p 3, 7 ? 4, m 2 and m 3 above (fig. 9), pA,m2 and m 3 below (fig. 10 ). There is 
no vacuity now in the series to show a true molar to have been shed, as it has 
been in so unusual an order. 
The next stage of dentition which I have observed in this species is the loss of the 
anterior premolar 7 ? 3, and the great wearing down of m 2 (fig. 11 ), and in one in- 
stance in the lower jaw m 2 was shed before p 3. 
The skull of a male Phacochcerus in the British Museum*', from the Cape de Verd, 
measuring 16 inches 6 lines in length, with the incisors of the Phac. ^lianl, viz. 
and the same broad and shallow posterior channel upon the canines shows 
the same numerical molar formula as No. 772, but the teeth are different in the upper 
jav/, they are 7 ? 3, 7 ? 4, m2 and m3; in the lower jaw they are p^, p A and m 3 ; both 
first and second true molars being shed in this jaw, whilst the last two premolars are 
retained. 
In the skull of a female Phacochcerus, 13|- inches in length, from South Africa, in 
the British Museum, but with the incisive formula of the Phac. JE,liani^ the molar 
* The term Phacochm'us Mthioflcus is retained for the species represented by this skull in the British 
Museum. 
