DUPLICIDENTATA. 367 
this species: ‘‘ Dark brown on the head, neck, shoulders, and sides 
passing into a deep black on the extremities, a very narrow white line 
passing backwards from behind the angle of the mouth to the shoulder ; 
under surface brownish ; the spiny hairs of the anterior part of the 
trunk flattened, grooved or ungrooved. The crest begins behind the 
occiput and terminates before the shoulders ; the hairs are long, slender 
and backwardly curved, the generality of them being about 43 inches 
long, while the longer hairs measure about six inches. 
“They are all paler than the surrounding hairs, and the individual 
hairs are either broadly tipped with yellowish-white, or they have a 
broad subapical band of that colour. The short, broad, spiny hairs, 
lying a short way in front of the quills, are yellow at their bases, the 
remaining portion being deep brown, whereas those more quill-like 
spiny hairs, immediately before the quills, have both ends yellow 
tipped. 
“The quills are wholly yellow, with the exception of a dark brown, 
almost black band of variable breadth and position. It is very broad 
in the shorter quills, and is nearer the free end of the quill than its 
base, whereas in the long slender quills it is reduced to a narrow mesial 
band. ‘The stout strong quills rarely exceed six inches in length, whilst 
the slender quills are one foot long. Posteriorly above the tail and at 
its sides many of the short quills are pure white. The modified quills 
on the tail, with dilated barb-like free ends are not numerous, and are 
also white. There are three kinds of rattle quills, the most numerous 
measure 0°65 inch in the length of the dilated hollow part, having a 
maximum breadth of 0°21 inch, whilst there are a few short cups 0°38 inch 
in length, with a breadth of 0°17 inch, and besides these a very few more 
elongated and narrow cylinders occur.’—‘ Anat. and Zool. Res.,’ p. 332. 
~ 
SUB-ORDER DUPLICIDENTATA—DOUBLE-TOOTHED 
RODENTS. 
These rodents are distinguished by the presence of two small 
additional incisors behind the upper large ones. At birth there are four 
such rudimentary incisors, but the outer two are shed, and disappear at 
a very early age ; the remaining two are immediately behind the large 
middle pair, and their use is doubtful; but, as Dallas remarks, ‘ their 
presence is however of interest, as indicating the direction in which an 
alliance with other forms of mammalia more abundantly supplied with 
teeth is to be sought.” 
Another distinctive characteristic of this sub-order is the formation of 
the bony palate,which is narrowed to a mere bridge between the alveolar 
