155—14 INDIAN TERTIARY AND POST-TERTIARY VERTEBRATA. 
Hastings from the upper eocene (oligocene) strata of the Hampshire basin. Two 
species were formed from these specimens, and it was shown at the same time that De 
Blainville’s Anthracotherivm velaunum must be referred to the new genus. Shortly 
before the publication of Professor Owen’s memoir, the new genus Ancodus had been 
established by M. Pomel, 1 for certain teeth which were subsequently shown to be 
generically the same as those described as Hyopotamus. There is no doubt that M. 
Pomel 3 s name has the priority, but as Professor Owen’s name is almost universally 
used in England it has been adopted here, although Ancodus is largely used by 
continental palaeontologists. 2 Subsequently other remains were described under the 
names of Bothriodon, Cyclognathiis, and Tapinodon , which were shown by Dr. 
Kowalevsky 3 to belong to Hyopotamus. It was also shown by the same writer that 
certain species referred to Cainotherium belonged to the same genus. 
In his original description it was at first considered by Professor Owen that 
Hyopotamus differed from Anthracotherium by the upper premolars having two 
1 barrels,’ in place of one, but it was subsequently shown that the teeth originally 
considered as premolars were in reality milk-molars. As was mentioned in the 
characters of the family, the whole number of the typical placental dentition is 
always present, but there is considerable diversity as to the position of the anterior 
premolars, and the relative size of the canines. Thus in H. leptorhynchus the 
first premolar is separated by a long interval from the other three teeth of that 
series, which are all in apposition, and the canine is large. In the form known as 
H. aymardi , which is very probably the female of the last, the first and second 
premolars are separated by 1 diastemse ’ of equal lengths from the third and fourth 
premolars, and the canine is small. In H. velaunus the first premolar only is separated 
from the others by a small ‘ diastema,’ and the canine is small. The skull, in those 
forms in which it is known, is remarkable for the elongation of the facial portion, 
for the smallness of the brain cavity, and for the absence of a ‘ larmier,’ (Filhol.) 
The upper true molars of the typical forms are distinguished from those of typical 
forms of Anthracotherium by the more distinct and wider loop formed on the outer 
border of the masticating surface at the union of the two outer columns. fThis 
difference is admirably shown in figures 6 and 9 of plate VII. of Professor Owen’s 
memoir , where the molars of Anthracotherium magnum (fi.g. 9J are reduced to the same 
size as those of Hyopotamus vectianus (fig . 6J.J There is, however, such a gradual 
transition, through less typical forms, from Hyopotamus to Anthracotherium in these 
respects, that it is almost impossible to give definite generic characters founded on 
the structure of the molar teeth, and it is not impossible, as previously observed, 
that the two genera may eventually have to be amalgamated. 
Distribution. — The genus Hyopotamus has a very extensive distribution in space, 
its remains having been obtained from the tertiaries of India, Europe, and North 
1 ‘Archives de la Bibliotheque de Genfeve,’ Vol. VII., 1847. 
2 Dr. Kowalevsky (‘ Phil. Trans.’ loc. cit., p. 22,) attempted to show that Ancodus was never defined, hut Dr. Filhol 
(“ Mammifores de Ronzon,” p. 87,) has shown that this is erroneous. 3 ‘ Phil. Trans.,’ loc. cit. 
