Genus A n u r o s o r e x ,1 A. M.-Edwards.
A n u r o s o r e x a s s a m e n s i s , Andr., Plate v, figs. 1—16.
Anurosorex assamensis, Andr. Ann. and Mag. Nat. Hist, 1875, vol. xvi. p. 282.
This remarkable modification of the ordinary type of Soricine structure was first
made known by Adolphe M.-Edwards in his admirable Memoir on the Fauna of
Tibet.
Before his description of the genus had reached Calcutta, Mr. S. E. Peal had
obtained in Assam, between Seebsaugor and Jeypur, in about 27° north latitude, a
small shrew-like animal remarkable for the great size of its head, its nude, scaly
extremities, and its extremely short, nude, scaly tail, which he forwarded to the
Indian Museum, Calcutta. I recognised it as a new generic form2 allied by its
dentition to Diplomesodon, Brandt.
The type of the genus, A. squamipes, A. M.-Edwards, is very abundant in the
plains and mountains of Tibet and Sé-tchouan, but as the physical characters
and climatológica! conditions of these two provinces of China are very different
from those which distinguish Assam, it was to be expected if the same generic
type occurred in Assam that it would present certain specific modifications on
its more northern féllow—a conclusion which is fully borne out by a careful comparison
of the two.
The structure of the ear, limbs, and tail has special reference to a burrowing
habit of the animal, the ear being valvular, so that it may be effectually closed
against the entrance of foreign substances, and the feet devoid of hair, but scaly,
and the tail reduced to very small dimensions. The eye also is excessively small
and buried deep in the dense silky fur. The hind feet, contrary to what is almost
invariably the case in burrowing mammals, are larger than the fore feet.
The Assam form appears to be considerably smaller than the Tibetan species, and
to differ from i,t in its proportionally greater head, slightly longer tail, and in the
fore feet not exceeding the hind feet in breadth and strength: moreover it is distinguished
by a differently coloured fur.
The semi-nude parts of the snout, the scaly limbs, and tail, are flesh-coloured.
The claws are yellow. The fur is set nearly erect, is fine, dense, and silky. I t is
longest on the rump, where it projects backwards a considerable way over the
tail, almost hiding it. Numerous strong hairs protrude beyond the general mass of
the fur, and are brown with obscure pale tips. Whiskers well developed. Shorter
hairs above and between the eyes. The general colour of the fur is dark slaty,
faintly washed with brownish rusty on the long hairs of the rump.
Total length: snout to vent, 2*92 inches; fore ‘foot, ’50; hind foot, ’75;
tail, -50.
1 Anurosorex, A M.-Edwards, Compt. Rend. 1870, lxx. p. 341, et Rech. des Mammif. 1868,-74, p. 264.
* Pygmura, Andr. Proc. Zool. Soe. Lond. 1873, p. 9.
Skull. The skull is not so elongated as in Pachyura, but it is more so than in
Soriculus mgrescens, and it is remarkable in being nearly half as long as the vertebral
column measured from the atlas to the end of the sacral vertebra. The
facial is relatively shorter to the cranial portion of the skull than in the former*
and these two regions bear about the same proportion to each other as in the skull
of the latter. The molar portions of the maxillæ have not the same lateral
expansion that they have in Pachyura, and in this respect the skull is also affiliated
to SoriculusI The greatest breadth of the cerebral portion, which is more
arched than in Paôhyura and Soriculus, is attained between the mastoid processes,
which are well developed and .project outwards and forwards in a marked
degree. The frontal is fuller than in any shrew I have examined, and the occipital
region is not directed so much forwards as in Pachyura and Soriculus. There
is a rather strong sagittal ridge with a small foramen on each side of its
anterior termination. The lambdoidal ridge is not very strongly developed. There
is an obscure, but at the same time easily recognisable, process in the' region corresponding
to. the post-orbital process. I t is placed at the posterior termination of a
short concavity in the outline of the orbito-temporal fossa, and defines a space corresponding
to the capacity of the orbit.
When viewed in profile, the parietal region is seen to be arched more than in the
generality of Soricine skulls, and that the anterior extremity of the sagittal ridge
terminates in a depression over the intër-orbital, temporal contraction, from which
point thè facial portion is arched forwards in a more marked degree than in Pachy-
ura or Crocidura, and, unlike these skulls, the nasals are not flattened above. In
this view of the skull the occipital region is nearly vertical. The palate is not sa
long, deep, or broad as in Pachyura, and increases in width from before backwards,
being prolonged behind the last molar and terminating in a sharp ridge with a
minute, acute, external process. There is only one anterior palatine foramen, without
any trace of a septum, and it is nearly as large as the infra-orbital foramen.
The mesopterygoid fossa is shorter and broader than in Pachyura or Sor ex, and is
somewhat lyre-shaped, broader in front than behind. At the junction of the basi-
occipital and basi-sphenoid, there is a central ridge with a slight depression on
either side of it, and it sends back a ridge to the external, anterior angle of the
occipital condyles.
The post-glenoid process is closely adherent to the outside of the posterior
extremity of the pterygoids which terminate in a hamular-like process, projecting
outwards and backwards, and it is widely separated from the glenoid surface for the
articulation of the upper section of the condyle. The post-glenoid process has the
foramen ovale completely hidden on its inner side by the arch formed by its
junction with the pterygoid, so that this foramen can only be seen in front.
This process, owing to the greater depth of the skull, is also at a lower level t h a n
in other Indian shrews, its lower margin being on a level with the lower third of
the front incisor, while in P . indica the lower margin of the process is on a higher
level than the posterior alveolar margin of the last molar but one. The anterior