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Show 1877.] MR. E. A. SMITH ON SHELLS FROM LAKE NYASSA. 721 ing's collection, said to have been from the Red Sea. The shell from Mozambique agrees perfectly with the type, except that the posterior end is rather less produced. I should add that the figure in the 'Conch. Icon.' considerably exaggerates the beaked appearance of this portion of the type shell. The lunule is elongate, narrow, and defined by a simple striation on each valve. 5. DONAX MADAGASCARIENSIS, Wood. Donax madagascariensis, Wood, Index Testaceolog. Suppl. p. 5, pl. 2. f. 3; Sowerby, Thesaurus, iii. pl. 280. f. 16; Reeve, Conch. Icon. viii. sp. 50. D. Keyii, A. Adams, P. Z. S. 1854, p. 87. Hab. Macusi River, near Quilimane, East Africa. The radiating striae and the ridges between them are much more strongly developed on the posterior cordiform area than on the anterior surface. On the other hand the oblique ridges on the latter portion of the shell are much stronger than on the former, where they become thin lamellae. The lines of growth are curiously present on the oblique costae, near the anterior ventral margin of the valves, but not visible in the interstices between them. 6. DONAX ^EMULUS. (Plate LXXV. figs. 23-25.) Shell small, triangular, somewhat elongate, very inequilateral, produced anteriorly, compressed and narrowly rounded, posterior area cordiform, not very acute at the margins, slightly sinuated at the middle ; radiately striate, except for a narrow space at the anterior dorsal slope; the strise are very fine, equidistant, those on the posterior area deeper and wider, with distinct intermediate lirulae, which are decussated by still more prominent obliquely ascending ones, which do not pass beyond the rounded carina; umbones acute, but little incurved ; interior dorsal slope rectilinearly sloping, posterior very suddenly inclined; ventral margin straightish ; lunule linear ; ligament small, prominent. Colour yellow, purplish, or cinereous, generally varied with darker concentric bands and purplish radiating rays, most distinct within the valves, which are more or less purple, generally white at the crenulated margins. Length 9| millims., height 6, thickness 4. Hab. Mouth of the Macusi River, near Quilimane. This pretty species reminds one very much of the West-African D. elongatus. However, it is a trifle shorter, has not the rugose line on the posterior area, nor the flatness in the centre of that part. EXPLANATION OF PLATES LXXIV. & LXXV. PLATE LXXIV. Fig 1, 2. Paludina jeffreysi, p. 716. Fig. 7. Lanistes affinis, p. 716. 3 3 4 capillata, p. 717. 8, 9. nyassanus, p. 715. 5(' e robertsoni, p. 717. 10, 11. solidus, p. 716. |