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Show 346 MR. E. A. SMITH ON SHELLS [Apr. 20, in some specimens is almost black, predominates ; and the opaque, obliquely somewhat zigzag stripes upon the back of the body-whorl in several shells are abruptly terminated in an oblique line which marks a period of growth. Between the larger creamy stripes which reach from suture to suture in the upper whorls, and extend over the whole extent of the last, there are minor streaks and spots flowing only a short distance beneath the suture. I feel much pleasure in naming this species (perhaps only a variety, but a very interesting one) after Professor Martens, of the Berlin Museum, who, amongst his innumerable and valuable conchological papers, has written several upon the fauna of the Nilotic region. 3. ACHATINA (LIMICOLARIA) RECTISTRIGATA. (Plate XXXI. fig. 2.) Shell oblong, cylindrically conical, narrowly perforate, whitish or of a pale rosy tint, varied with oblique brown stripes, which at times become broader or blotchy at the lower part of the whorls. The latter are 8 in number, rather convex and slowly enlarging, obliquely striated by the lines of growth, divided by a simple subhorizontal suture. Last volution oblong, a little attenuated at the lower part. Aperture inversely subauriform, whitish or pale rose within, equalling rather more than one third of the entire length of the shell. Peristome (viewed laterally) oblique, a little tortuous, thin at the edge, and inconspicuosly thickened within. Columella spirally contorted, bluish, and reflexed over the perforation at the upper part, brownish inferiorly, and gradually curving into the basal margin of the aperture. Paries coated with a thin callosity. Length 44 millims., diam. 17 ; aperture 16 long, 8 wide. The peculiarity of this species consists in the ornamentation taking the form of defined stripes, and not exhibiting a wavy or zigzag tendency so common to most of the species of this group of Achatina. L. cailliaudi, Pfeiffer, and L. sennaariensis, Shutleworth, are allied forms. 4. BULIMUS (BULIMINUS) PTYCHAXIS. (Plate XXXI. fig. 3.) Shell elongate, turreted, perforate, thin, dirty white, covered with a very thin, pale, sordid olive epidermis. Spire elongate-conical, with a rather obtuse apex. Whorls 9, somewhat convex, divided by a deepish suture, bearing fine, regular, oblique and slightly flexuous costulae, which, upon the last whorl, become less pronounced from the middle downwards. Aperture vertical, occupying about one third of the length of the shell. Columella erect, reflexed over the umbilicus, bearing a fine oblique plait a little below the middle ; outer lip thin and feebly expanded. Length 27 millims., diam. 10£ ; aperture 9 long, 5 broad. B. kirki of Dohrn, from Mozambique, is sculptured very similarly to this species. It is, however, much shorter, and does not possess a columellar fold. The latter is even more distinct in the young shell than in the adult; and the last whorl in the former exhibits a faint |