Page:Transactions NZ Institute Volume 2.djvu/39

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In quoting the numerous authorities describing the species, Dr. Günther, amongst others, includes:—Penn., British Zool., iii., p. 216, pl. 30; Knox, Edin. Journal; Nat. and Geo. Society, ii., p. 427.

Thus the material for scientific observation in the British Museum is extremely limited, with regard to the Xiphiidæ. I may here remark, that in my brother's (the late Professor Robert Knox) description, the comparative anatomy would, to a certainty, be given; and if so, I would have thought Dr. Günther would have availed himself of it.

The portion of the integuments, placed in the Museum, occupied the anterior part of the dorsal line, corresponding to the neck, reaching from the head, to and past the dorsal fin. I observed no appearance of scales; the whole resembling coarse leather, and so formed as to require a saw to cut it. The tissue thus forms a regular coat of mail made of spiculi of bone so interwoven with the integumentary tissues, as to be completely concealed. I should consequently, imagine this fish to be perfectly secure from any enemy, in or out of the water.

The dorsal fin is, undoubtedly, a striking feature in the Xiphiidæ, and the caudal fin, in the specimen to which I have alluded in my brother's collection, was also prominent. At a first view, it was as if formed of two dorsals, and if included in the length of the fish (which is generally done by naturalists), would have added a foot or more to the total length.

By the very limited observation I could make on the specimen now under review, owing to the non-scientific dissection it had been subjected to before I got it, I found the dorsal fin capable of being moved, to a very considerable extent, in all directions. The interspinal processes (b, Plate 1) are firmly united to each other, presenting a free articular surface to the rays of the fin; and when acted upon by the powerful muscles of the back, will act as a sail, and an oar, the brain being the steersman, the tail, no doubt, answering the cerebral instinct, voluntary or not. The longitudinal fissure seen in the specimen is not the result of dissection, but natural; and is lined by a delicate soft membrane, a continuation of the same covering immediately investing the rays of the fin. The spinous processes of the vertebræ, when examined, will be found bifurcated (c, Plate 1), forming a groove or slide for this unique action of the dorsal fin in the Xiphiidæ. In many fishes, however, the spinous rays can be depressed, and again erected, at the will of the fish.

The following measurements and weights of the specimen now deposited in the Colonial Museum, were observed before and after their preparation:—