1847.] OWEN ON ENGLISH EOCENE MAMMALIA. 37 
which I have associated, as members of the same great natural group 
of mammals*, the extinct genera Hippohyus, Hyracotherium, Chero- 
potamus, Anthracotherium, Merycopotamus, Dichobunes and Anoplo- 
therium, although the symmetrical or parial character of the crown of 
the tooth, as shown by the normal lobes o 7, and o! 7 (PI. ITT. fig. 5), in 
Anoplotherium is disturbed by the excessive development of the acces- 
sory tubercle p. 
The fossils about to be described give evidence of the former exist- 
ence of another of these interesting annectent links that once filled up 
the interval that now almost insulates the Ruminants from the few 
remaining members of the Ungulates with the lobes of the grinders 
and the toes of the feet in symmetrical pairs. These fossils, dis- 
covered by Alexander Pytts Falconer, Esq., in the eocene sand-bed at 
Hordle, consist of a portion of the upper jaw, with the three true 
molars, the third and fourth premolars, the canine and three incisors ; 
and a nearly entire under jaw, with the whole dental series of one side 
and a large proportion of it on the opposite side (PI. IV. figs. 2, 3, 4, 5). 
The genus established by the peculiarities of this dentition, and which 
I propose to call Dichodon+, makes the nearest approach by its upper 
true molars to the Merycopotamus of Messrs. Cautley and Falconer 
(Pl. IV. fig. 7), and to that smaller allied extinct Indian quadruped 
called ‘ Anthracotherium silistrense’ in the second volume of the 
Second Series of the Geological Transactions (p. 392, pl. 45. figs. 2 
& 3). 
In the true molars of the lower jaw the genus Dichodon closely re- 
sembles the genus Dichobune ; and it manifests a striking affinity to 
the Anoplotherioids in the low development of the canine teeth and 
in the number and uninterrupted contiguity of the entire dental series. 
But Dichodon presents peculiar modifications of the molar and espe- 
cially of the premolar teeth, which distinguish it from all known 
genera of fossil and recent Mammalia. 
The crowns of the upper true molars of Dichodon (PI. IV. fig. 3. 
M 1, 2 & 3) are subquadrate and four-lobed, and the antero-posterior 
cleft describes two strong curves, concave outwards, as in fig. 3. pl. 45. 
of the ‘Geol. Trans.’ above-cited, and as in Merycopotamust (PI. IV. 
fig. 7) and Dichobunes§ ; but there is no depression or fold of enamel 
that would mark off in the abraded crown a lobe of dentine answering to 
that marked p in fig. 1. p.420 of the ‘ Geol. Proceedings’ above-cited ; 
and by this difference, as well as other characters, the molars of 
Dichodon more resemble those of Merycopotamus and of the little 
so-called Anthracotherium silistrense. 
The outer sides of the outer lobes (fig. 2. 0', 0) of Dichodon are 
* Odontography, pp. 523, 571. . 
+ The numerous sharp and well-defined divisions of the crowns of hoth upper 
and lower molar teeth suggested the term ‘ Dichodon’ (d:ydw, divido; ddods, dens), 
expressive of this character, and of the sharp incisive nature of most of the teeth; 
the human cutting-teeth were called dvyaoripes d0d6yTes, incisivi dentes, by the 
Greek anatomists. 
~ Odontography, p. 566, pl. 140. fig. 8. 
§ Proceedings of Geol. Society, May 1846, p. 420, fig. 1. 
