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Show 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 F. spinosissima. DESCRIPTION OF THE PLATES. PLATE LVI. Fig. 1 represents a portion of the skeleton of the dermal system of Alcyoncellum speciosum, as seen in situ on a 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 terminations of each of the reticulating spiciila, 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 rejsresents one of the slender attenuated rectangular sexradiate spicula of the skeleton interstitial structures, X 175 linear. Fig. 2. T w o of the slender rectangulated sexradiate dermal spicula as seen in 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, X 80 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 development, attached either to the fibres of the skeleton or to the translucent interstitial membranes, X 80 linear. PLATE LVII. Fig. 1 represents a small portion of the stout and beautifully regular dermal reticulation of Farrea valida, with its numerous rectangulated sexradiate defensive organs based on the fibres, with a portion of the slender reticulated skeleton beueath it, X 61 linear. Fig. 2. A small portion of the dermal reticulation, exhibiting more distinctly the structure aud 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, exhibiting the mode of disposition of the spinous defensive prickles coated with sarcode, X 80 linear. 6. On the large Sheep of the Thian Shan, and the other Asiatic Argali. By Sir VICTOR BROOKE, Bart., F.Z.S., and BASIL 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. S. 1874, p. 425), and the true Ovis poli of Blyth from the Great Pamir, we have been induced to study |