1875.| sir VICTOR AND MR. B. BROOKE ON ASIATIC SHEEP. 509 
A few such prickles as described above occur in F. spinifera; but 
the greater size of the skeleton-fibres and their more compact and 
regular mode of arrangement, their large and very distinct canals, 
at once distinguish that species from I’. spinosissima. 
DESCRIPTION OF THE PLATES. 
Puate LVI. 
Fig. 1 represents a portion of the skeleton of the dermal system of Alcyon- 
cellum speciosum, as seen in situ ona piece of Dr. Miller’s specimen 
of the sponge mounted by him in Canada balsam, exhibiting the mode 
of arrangement of the slender rectangulated sexradiate spicula, with 
the floricomo-sexradiate defensive ones attached to the distal termina- 
tions of each of the reticulating spicula, x 36 linear. In plate xxiv. 
P.Z.S. for 1869, fig. 11 represents one of the floricomo-sexradiate 
spicula X 666 linear; fig. 10 one of the dermal simple rectangulated 
sexradiate spicula to which the floricomo-sexradiate ones are attached, 
x 108 linear; and fig. 9 represents one of the slender attenuated rect- 
angular sexradiate spicula of the skeleton interstitial structures, x 175 
linear. 
Fig. 2. Two of the slender rectangulated sexradiate dermal spicula as seen iz 
situ, showing the mode in which the lateral radii pass freely over 
each other, so as to allow of the expansile action of the dermal system, 
x80 linear. 
Fig. 3. A small piece of the skeleton-fibres of the sponge immediately beneath 
the dermal system, with numerous gemmules in various stages of deve- 
lopment, attached either to the fibres of the skeleton or to the trans- 
lucent interstitial membranes, x 80 linear. 
Puate LVII. 
Fig. 1 represents a small portion of the stout and beautifully regular dermal 
reticulation of Farvea valida, with its numerous rectangulated sexra- 
diate defensive organs based on the fibres, with a portion of the 
slender reticulated skeleton beneath it, x 61 linear. 
Fig. 2. A small portion of the dermal reticulation, exhibiting more distinctly 
the structure and mode of disposition of the rectangulated sexradiate 
defensive organs, X 80 linear. 
Fig. 3 represents a small piece of the skeleton-structure of Farrea spinosissima, 
with its numerous attenuated defensive spinous prickles, x 36 linear. 
Fig. 4. A small portion of the fibre of the sponge, more highly magnified, ex- 
hibiting the mode of disposition of the spinous defensive prickles 
coated with sarcode, x 8() linear. 
6. On the large Sheep of the Thian Shan, and the other 
Asiatic Argali. By Sir Vicror Brooks, Bart., F.Z.S., 
and Basin Brooke, F.Z.S. 
[Received June 14, 1875.] 
Captain Biddulph having shown (antea, p. 157) appreciable 
points of distinction between the large Wild Sheep obtained by the 
officers of the Yarkand Mission on the Thian Shan, described by 
Dr. Stoliczka as Ovis poli (P. Z.S8. 1874, p. 425), and the true Ovis 
poli of Blyth from the Great Pamir, we have been indueed to study 
