528 
ORIGINAL ARTICLES. 
"besides the points of difference to be noticed in treating of the Milk 
series [§ 8, 1], the fact that in both the jaws the fourth tooth is in 
place, while the alveolus behind it shows that the fifth, or m 1, was 
still in the gum, is a conclusive proof that the teeth they contain do 
not belong to the permanent dentition. For in the recent, as 
the fossil Rhinoceros m 1 is always in place a considerable time 
before Pm 4, and is always more worn. # Neither in the skulls 
at St. Petersbnrgh, ranging from young to old adults, nor in the 
jaws in the Oxford and British Museums, of all ages, is there the 
slightest vestige of Pm 1, but its place is represented by a rough 
crest, (cristula aspera of Brandt.) Nor in the four lower jaws, con¬ 
taining deciduous dentition, which I have sawn up, have I detected an 
alveolus or other trace of its germ. On the contrary, the fangs of 
the first milk molar, are so close together, and in stoutness and 
length so entirely different from the rest of the milk set, that there 
is very good presumptive evidence that in the lower jaw Pm 1 is not 
calcified even in the youngest Rhinoceros. The dental formula 
therefore, as far as our present knowledge goes, will be Dm t» 
Pm 3 . m 3 
Pm 3 . m 3 
§ 5. Characteristics of Permanent Upper Molar Series.— 
The teeth of the Upper Molar series most difficult to be determined on 
account of the variable form of the costse, valleys and colles consequent 
on different stages of wear, increase in size from the first Premolar 
(Pm 2) up to m 2 where a maximum of development is reached. 
The entrance of the anterior valley (A) also descends from before 
backwards, viewed in relation to the size of the tooth until in m 3 it 
is situated but OT to 02 inches from the base of the crown. Gene¬ 
rally in the Premolars it is blocked up by a small cusp and often in 
the true molars. On the grinding surface of the crown, a process of 
enamel thrown inwards and slightly backwards from the exterior 
lamina t [L of fig 1—4] meeting a corresponding process thrown for¬ 
wards and slightly outwards from the middle of the median collis 
intercepts the posterior portion of the anterior valley. The former 
(Gr) of these is the Anterior , the latter (H) the Posterior ‘ Combing 
Plate.’ Sometimes they are fused together at their junction, com¬ 
pletely insulating the portion (C) of the valley they cut off, some¬ 
times they merely touch, or leave a small interstice communicating 
with the main portion of the anterior valley. In the bicorn rhino¬ 
ceros of J Sumatra the anterior combing plate is always absent, as 
also in those teeth which Cuvier and Professor Owen figure as JR. 
* In a skull of R. Sumatranus (2936 of the Hunterian Catalogue) m 1 is 
beginning to be worn, while the whole of the milk molars are still in place. It 
belonged to an animal considerably older than the Thame, or Lawford Rhinoceros. 
f ‘ Collis externus,’ Brandt. ‘ Colline Premiere qui suit exactement le bord,’ 
Cuv. 
J Vide 2935. Mus. Coll. Surg. 
