94—60 INDIAN TERTIARY AND POST-TERTIARY VERTEBRATA. 
9. Hyotheeium waterhousi^ (Pom.). Low. miocene, France. 
Amphtchcerus major, Brav. PalcBochoerus major, Pom. 
Hyotherium majus, Filh. Palceochcerus waterhousi, Pom. 
A species coming next in size to H. mmmeringi, but with molars of the simple 
structure of H. typus ; which it considerably exceeds in size. The inner pair of 
upper incisors are unusually large. 
A^nities. — If the above-mentioned European species be referred to two genera, it 
appears that H. soemmeringi is the only one which should belong to Tlyotherium ; all 
the rest belonging to Palwoclmriis. The former species, by the more complex 
structure of its molars, serves to connect the other species with the less specialized 
forms of Sus.^ From the phosphorites of Quercy Dr. H. FilhoP is about to describe 
the cranium of an allied form under the new generic name of Doliochoerus, In that 
genus the molars are of very simple structure, the last upper molar having no 
distinct talon, and the parietal portion of the cranium being extremely unlike that 
of Sus ; from which it may be concluded that the genus belongs to a very primitive 
type. In the tertiaries of North America remains of numerous pig-like animals 
have been discovered apparently connecting Bgotherium with Vicotyles : several of 
these species have been referred to the two new genera Chcenohyus and Thinohyus^^ 
whose relation to the other genera is exhibited in the following table, viz.\ — 
Dicotyles. Pm. f ( pm. 2 in contact with pm. 3 ). 
CiiiENOHYUS. Pm. I (pm. 2 isolated). 
Thinohyus. Pm. f ( pm. 1 isolated). 
Hyotherium. Pm. | ( pm. 1 in contact with pm. 2 ). 
The four genera are considered by Prof. Cope to be closely allied ; and the 
fossil forms connect Dicotijles so closely with Sus, that in a paheontological classification 
it seems impossible to refer those two genera to distinct families. F rom the study of -the 
skull of TI. ivaterliousi Dr. FilhoP has been led to the conclusion that it is improbable 
that Hyotherium is the direct ancestor either of Dicotyles or Sus ; but it is most 
probable from the structure of its molars that it must have been intimately related 
with such ancestral stock. The later preniolars are relatively stouter than in existing 
species of Sus. The canines are small, and in II. soemmeringi the root of the upper 
one is double : there is no distinct diastema, and (at least in several species) the 
lower canines had not attained the peculiar form of those of Pus. 
Distribution. — It is only recently that the genus has been recorded from 
1 Vide Eilhol, ‘ Ann. Sci. Geol.,’ vol. XI., pis. IV. -IX. 
2 Identified with this species on the authority of Dr. Eilhol [op. cit., p. 19) : it is identified by Peters [op. oil., p. 136) 
with II. soemmeringi. 
3 Gaudry, “ Les Enchainements— Mam. Tert.,” p. 71. 
4 The present writer is indebted to Dr. Eilhol for early information concerning this undescribed genus, and also for 
proofs of the illustrations to accompany ^his forthcoming memoir upon the same. 
5 Cope, ‘■Pro. Amer. Phil. Soc.,’ vol. XVIII., p. 373, 1879. Talmochoerus condoni. Marsh, .should he referred to 
riaiggornis or Thinohyus, according to Prof. Cope. 
6 ‘ Ann. Sci. Geol.,’ vol. XI., p. 81. 
