1889.] MR. 0. THOMAS ON A NEW GENUS OF MURID&. 247 
black eyes. Mr. Fisk said there are also three white specimens of 
this animal in the Capetown Museum. 
A letter was read from Dr. E. C. Stirling, of Adelaide, containing 
a copy of his description of a new Australian Mammal (which had 
already appeared in nearly the same form in ‘ Nature,’ vol. xxxviil. 
p- 583), as read before the Royal Society of South Australia, Sept. 4th, 
1888, and published in that Society’s ‘Transactions.’ Dr. Stirling 
was now engaged in finishing a complete description of this very 
peculiar and interesting burrowing animal, which somewhat resembled 
a Cape Mole (Chrysochloris) in general external appearance, and 
expected to be able to communicate it to this Society when ready. 
Mr. Seebohm exhibited the skin of a male example of Phasianus 
- chrysomelas which had been purchased in the flesh (along with a 
female) in Leadenhall Market, where several others were also sold, 
and was stated to have been sent over in a frozen state from the 
Trans-Caspian provinces of Russia. 
The following papers were read:— 
1. Description of a new Genus of Muride allied to Hydromys. 
By Oxprinip Tuomas, Natural History Museum. 
[Received March 26, 1889.] 
(Plate X XIX.) 
One of the most singular and at the same time most isolated genera 
of Muride is Hydromys, of which the only species is the well-known 
Australian Water-rat. Alone of the family, and, with one exception’, 
alone of the Rodentia, this remarkable animal has only two molars 
on each side of each jaw, and the structure of these molars is at the 
same time quite different from that found in any other known Rat. 
Externally Hydromys has taken on characters suitable for a purely 
aquatic life, standing, so far as regards external specialization for 
swimming, in an intermediate position between Potamogale and Nec- 
tomys”, less specialized than the former and more so than the latter. 
The skull of Hydromys differs from other Muridz in many 
characters, and especially in the structure of the infraorbital foramen, 
which is hardly murine in the ordinary sense at all, as it is of about 
the same breadth above and below, and its external wall has not the 
anteriorly projecting plate found in the great majority of the Rats 
and Mice (see Plate XXIX. fig. 7). 
Altogether Hydromys has occupied a peculiarly isolated position 
in the family, no other genus showing any approach towards it, and 
there is therefore a proportionate amount of interest in the discovery 
of a new form allied to it. The proof of alliance lies wholly in the 
1 Heterocephalus phillipsi, see P. Z. 8. 1885, p. 847. 
* Peters, Abh. Ak. Berl. 1860, p. 152. Regarded as a subgenus of Holochilus, 
Thomas, P. Z. 8. 1882, p. 101. 
17* 
