OCR Text |
Show 1880.] FROM CENTRAL AFRICA. 349 olive, the front of the body-whorls being more or less stained by reddish earthy deposit. The spines and the keel are also of a browner tint than the rest of the shell. Length 45 millims., greatest diameter 34 ; aperture 35 long, 16 broad. This is perhaps the most remarkable species of freshwater Mollusca yet discovered. Its strange form, the array of spines at the angles of the volutions, the prolonged beak, the pretty sculpture, and the lack of an epidermis give this shell a unique character among all others. The number and proximity of the spines vary in different specimens ; the largest shell has the unusual number of fourteen on the last whorl, five of them being quite close together near the aperture. One example differs from the rest in having a narrow olivaceous line around the middle of the body-whorl. NEOTHAUMA1, nov. gen. Shell like that of the genus Vivipara, but having the aperture effuse and slightly channelled at the base, and the outer lip rather deeply yet widely sinuated in the middle. Animal and operculum unknown. The aperture in the genus Vivipara is, as a rule, more or less circular or ovate, and the continuous peritreme is generally almost level or on one plane. In the present genus on the contrary, the form of it is irregular and angular, and the labrum is deeply emarginate, causing the level of the peristome to vary considerably. 10. NEOTHAUMA TANGANYICENSE. (Plate XXXI. figs. 7-7c.) Shell ovate, acuminate, solid, scarcely rimate, white, clothed with an olive-brown epidermis. Young shells exhibited two brown bands upon the upper whorls and three on the last. Whorls 7, roundly shouldered above, obliquely convexish at the sides, separated by a very deep horizontal suture, sculptured with oblique flexuous lines of growth and a few faintly impressed spiral striae. Last whorl (with one exception) angular and keeled at the middle. Aperture irregularly triangularly ovate, bluish white within, effuse at the base. Columella thick, slightly arcuate, white; callus reflexed, almost concealing the umbilical perforation, joining the upper extremity of the outer lip; the latter is thin, a little angular in the middle at the termination of the keel around the whorl, and when viewed laterally is seen to be deeply and widely sinuated. Length 53 millims., diam. 29 ; aperture 24 long, 19 broad. Another specimen, length 46 millims., diam. 29 ; aperture 23 long, 19 broad. The largest specimen whose dimensions are given above is of abnormal growth, and exhibits scarcely any trace of the strong angle and keel which is so characteristic of the species. The colour bands are distinct in the young shell, but with age entirely disappear. 11. PLANORBIS SUDANICUS, Martens, Mai. Bliit. 1870, p. 35, 1874, p. 41 ; Novitates Conchyl. vol. iv. pl. 114. f. 6-9. This species is very like the West-Indian P. guadelupensis, but 1 From veos, new, and 9avpa, a wonder. |