70 Mr, O. Thomas on 
striated, the striation is essentially different from that in 
Lemniscomys, the middle line here being light with an even 
number of black lines external to it, while in both Lemnis- 
comys and, if a line is present, in Arvicanthis, the middle 
line is black, thus altering the whole pattern. 
So far as is known, there are four definite dark lines in all 
the species of Rhabdomys, no variation in the number or 
continuity of the lines occurring in the genus. But in 
desert forms, such as BR. p. bechuane, they are considerably 
reduced in intensity. 
A paper on the forms of Rhabdomys was published by 
Mr. Wroughton in 1905 *. 
VII.—On Rattus as a Generic Name, with a Note on the 
Nomenclature of Echimys and Loncheres. By Oupririp 
THOMAS. 
(Published by permission of the Trustees of the British Museum.) 
In Palmer’s ‘Index Generum Mammalium,’ 1904, the 
standard work on mammalian generic names, Rattus is first 
quoted (p. 601) as from Frisch, 1775, and then (p. 602) as 
from Donovan, 1827, with a note to the latter that it “is 
entitled to recognition if Rattus, Frisch, 1775, is not a valid 
name.” Palmer also notes that Rattus, Zimmerman +, “is 
not generally regarded as a valid generic name,” a conclusion 
with which I concur. Frisch’s names are also now refused 
recognition {, and therefore the question arises as to the 
animal to which, if any, the name Rattus is applicable. 
Palmer’s, and later on Miller’s, belief that Donovan’s use 
of the name is the first valid one does not prove to be correct, 
for it was used in valid form by Desmarest in 1822 (Mamm. 
ii. pp. 297-300). Though placed in the synonymy of dus, 
its type, settled by tautonymy, would clearly be Mus—or, as 
now called, Epimys—ratius, Linn. 
Fortunately, however, I have been able to find a still 
earlier use of the name, which does not upset, as Desmarest’s 
would, the now widely used Epimys, but falls on a rare and 
little-known Paraguayan animal, the “Rat épineux ” of Azara. 
* Ann. & Mag. Nat. Hist. (7) xvi. p. 629. 
+ Spec. Zool. Quadr. p. 344 (1777). 
t Cf. Thomas and Miller, Ann. & Mag. Nat. Hist. (7) xvi. p. 461. 
