250 Mr. Forbes on the Land and Freshwater is a little more in proportion to the white, and in some indi-viduals the bill is furnished with* two processes in the upper mandible, like the young of the preceding species, except that the bars on the two middle feathers in the tail are continuous. Note. — The day after the above paper was read, two mature specimens were received from Iceland ; they are male and female, and have just come through the moult, and cor-respond exactly in the markings with the breeding individuals brought by Mr. Proctor ; they are, however, a little brighter in colour, occasioned principally by the freshness of the plu-mage, and certainly do not vary more than might be expected from the difference in the young from the same nest. I may also observe that all the mature specimens I have seen from Iceland, amounting to seven in number, have the upper man-dible furnished with two processes ; whilst in the many Green-land specimens I have examined, only two have had the dou-ble process, and these were apparently very old individuals. EXPLANATION OF THE PLATE. A. Tail-feather of young Falco Islandicus. B. Primary of mature ditto. D. Lesser wing-covert feather of ditto. E. Primary of mature Falco Grcenlandicus. F. Tail-feather of young ditto. G. Covert feathers of mature ditto. XXVIII. — On the Land and Freshwater Mollusca of Algiers and Bougia. By Edward Forbes, [With Plates*.] During a visit to the regency of Algiers in May 1837* I ob-tained forty-five species of land and freshwater Mollusca, chiefly collected in the neighbourhoood of the city of Algiers and of the town of Bougia (in the province of Constantine). M. Mi-chaud, a distinguished French naturalist, published the year before a pamphlet entitled, i Catalogue des Testaces vivans envoyes d 5 Alger, par M. Rozet/ in which he enumerates twenty-five species of land and freshwater shells ; but a great part of these are not correctly speaking from Algiers, but from Oran (near Morocco), where the Fauna of Barbary assumes a different aspect, approximating to that of the Canaries on the one hand, and to that of Spain on the other. * These plates will form part of the Supplement.
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