SAGJIATIIERIUM ANTIQUUM. 
87 
is the larger ; they seem to be the protocone and tritocone of Scott’s nomenclature, 
'fhe most peculiar feature of these teeth is, that from the postero-external cusp a ridge 
runs along the posterior border of the tooth, and when worn gives rise to a surface 
continuous with the ectoloph. It seems probable that this posterior ridge belongs to 
the cingulum, and may include elements equivalent to the metastyle and hypostyle ; it 
does not seem to bo comparable to the metaloph of the molars. The antero-internal 
cusp is large and V-shaped, the anterior arm of the V running forwards and outwards 
towards the parastyle, while the posterior arm extends outwards and backwards to the 
postero-external cusp, and seems to include a distinct element. It is probably from 
the increase in size of the latter, and of a minute cusp here situated immediately behind 
the inner end of the antero-internal cusp, that the metaloph of the molariform premolar 
of the later forms has arisen. At the same time it should be observed that in 
Megalohyrax the premolars are much more nearly similar in plan to the molars than 
in Saghatherium, and the change there required to convert the posterior premolar into 
a tooth similar to the anterior molar would be a slight one. The minute postero- 
internal cusp above referred to can be seen in the second, third, and fourth premolars, 
but is largest in the last. The anterior premolar differs somewhat from the others. 
Its outer wall, as in them, consists of three elements, viz. a large parastyle forming the 
anterior angle of the tooth, and behind this a protocone and tritocone. From the last- 
named a ridge, apparently composed of two cusps (I metastyle and hypostyle), forms 
the posterior border of the tooth. The antero-internal angle of the tooth is occupied 
by a large cusp (deuterocone) borne on a separate root. In the type specimen, in 
front of the anterior premolar are the broken roots of the canines [c.) ; the larger 
posterior root is oval in section, the anterior nearly circular. The series of cheek- 
teeth, as a whole, forms a curved line. The two last premolars are wider from within 
outwards than from before backwards ; the second is nearly square. 
No specimen of the mandible in which the teeth of the symphysial region are 
preserved is known ; but in one in which the symphysis is present the roots or 
the alveoli of these teeth can be seen, and from these it appears that there were 
probably three pairs of procumbent incisors, of which i. I and i. 2 were larger 
than i. 3. All form a closed series and were not separated by any iirterval from those 
of the opposite side. The canine was a one-rooted tooth separated by a very short 
diastema from the anterior premolars. The two anterior premolars are each borne by 
two transversely oval roots ; the third and fourth by three roots, of which two are 
anterior, while the third or posterior one is transversely elongated. In no specimen is 
the crown of the first premolar preserved. The other premolars each consist of a 
pair of V-shaped columns, the anterior arms of the V’s being much the longer ; 
the posterior arms are placed almost transversely across the crown. At the anterior 
(‘nd of the anterior V there is a small tubercle which projects backwards and partly 
closes the opening of the V. This seems to be the parastylid of Osborn’s 
