978 DR. C. I, FORSYTH MAJOR ON A [Dec. 1, 
the frontal joins the maxillary, thus separating the lachrymal and 
nasal; and, besides, there is such a variability in the size and 
mutual connections of the bones in this part of the skull in young 
specimens, and, to a certain extent, in adult ones as well (four 
nasals, obliteration of the Jachrymo-frontal suture, &c.), that we 
cannot here enter into more particulars. 
My purpose was to show that, in respect of the above characters 
also the Malagasy Hippopotami are intermediate between H. siva- 
lensis and H. amphibius, and appear io be in close relationship 
with both. Occasionally young specimens are hexaprotodont, as 
the Siwalik forms. 
I think that, from what I have stated, we are fairly entitled to 
surmise that the Hippopotami entered Africa at a time when they 
were still in possession of all the characters of the Siwalik species, 
and that they crossed over to Madagascar when they had reached a 
condition intermediate between H. sivalensis and H.amphibius. In 
this condition they persisted in Madagascar, whilst on the neigh- 
bouring continent they progressed (or retrogressed) farther in the 
same direction. It is a curious circumstance that the Hippopo- 
tamus major from the Upper Pliocene of Italy has gone beyond 
H. amplibius in the same specialization; this may have had 
something to do with its earlier extinction. 
RopENTIA. 
But little attention has hitherto been paid to the Rodent fauna 
of Madagascar. Although four or five more or less nominal genera 
had been founded, it has been surmised that the Malagasy Rodentia 
have immigrated in recent times and are not even specifically 
Madagascar genera. This supposition rests on the assumption that 
the Rodents are, as a rule, passively wandering (Wallace, Zittel), 
and was made in spite of Peters having long ago pointed out that 
Nesomys, the first known Malagasy Rodent, resembles the American 
Hesperomyes in the conformation of the enamel and in the pro- 
portions of its molars *. 
My collections contain some hundred specimens of Rodentia, 
belonging to five genera and eight species, five or six of the 
species and two genera being new, besides two new genera found 
in a fossil condition. This material I have begun to work out, 
and, although my investigations are far from being completed, I 
do not think that the following conclusions will hereafter have to 
be modified in their main points. 
The great majority of Malagasy Rodents at present known, viz. 
the genera Nesomys, Hallomys, Gymnuromys, Eliurus, Brachy- 
1 « Hine neue Gattung der Murinen aus Madagascar, welche in dem Zahnbau 
sich am nichsten den Hesperomys der westlichen Hemisphare anschliesst, und 
so ein neues Beispiel yon der geographisch so merkwiirdigen Verwandtschaft 
der Fauna yon Madagascar mit der von Amerika liefert...... Die Backziihne 
= in ihrer Schmelz bildung und Proportion ahnlich denen von Hesperomys.’’ 
(Sitzungsber. Ges. naturf. Freunde Berlin, Oct. 18, 1870, pp. 54, 55.) 
