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Show 368 MESSRS. MACDONALD AND BARRON [May 28, among the most fortunate of recent carcinological observations. Their great size would well adapt either of the species for culinary purposes if any one could be induced to acclimatize the species to our own lakes and streams. This appears to be the more easy in regard to the species from America, since the Lake Amatitlan is at so lofty an elevation as to be of a very low temperature. DESCKIPTION OF PLATES XXX. & XXXI. PLATE XXX. Macrobrachium americanum. c. Rostrum, b. Superior antenna*;, c. Inferior antennae, d. Mandible, h. First pair of pereiopoda. v. Posterior pair of pleopoda. z. telson. PLATE XXXI. Fig. 1. M. formosense. c. Scale of inferior antennae, v. Posterior pair of pleopoda. z. Telson. 2. M. longidigitum. c. Scale of inferior antennas, v. Posterior pair of pleopoda. z. Telson. 3. M. africanum. c. Scale of inferior antenna?, v. Posterior pair of pleopoda. z. Telson. 5. O n a supposed new species of Galeocerdo from Southern Seas. By J. D. M A C D O N A L D , M.D., F.R.S., and Mr. C H A R L E S B A R R O N , Curator of the Haslar Museum. (Plate XXXII.) The following observations on a species of Galeocerdo, from the Australian coasts, are based on two jaws and a portion of skin preserved by F. M. Rayner, Esq., Staff-Surgeon, R.N., together with notes and measurements made by him, and drawings made by Dr. J. D. Macdonald, R.N., from the recent animal. On reviewing the literature of the genus Galeocerdo it would appear that, comparatively, few specimens have actually been obtained for scientific examination, as the great authorities on this group of fishes, Miiller and Henle, only mention two examples of the southern Tope (G. tigrinus), and two of the northern (G. arcticus), with several jaws ; and the British-Museum Catalogue of the Chondropterygii only includes one specimen of the former and three jaws of the latter species. When we compare the external characters of the two known species, as given and depicted by Muller and Henle, with those of the present Shark, we find the proportions of the body and fins of G. arcticus (Muller and Henle, pl. 24) to agree best with it; but in the colour of the skin there is great difference, and the scales represented in the plate alluded to are approximated and slightly imbricated, besides being relatively broader and more distinctly three-keeled than those of our fish. Moreover, although the teeth figured |