OCR Text |
Show 1881.] LAKES TANGANYIKA AND NYASSA, ETC. 283 the author are those of an adult specimen; and the aperture is proportionally longer. In the present species the coloration is rather different, and the epidermis is of an olive tint instead of rich fulvous brown. 15. ACHATINA CRAVENI. (Plate XXXIII. fig. 11.) Achatina kirkii, E. A. Smith, Ann. & Mag. Nat. Hist. 1880, vol. vi. p. 428. Shell elongate ovate, somewhat acuminate above, beneath a yellowish epidermis white, ornamented with suberect, slightly wavy, brown stripes. Whorls 8-9, rather convex, rather coarsely gra-nosely sculptured ; suture between upper whorls horizontal, between two last more oblique ; last whorl descending, smoother upon the lower part. Aperture subpyriform, bluish white, occupying less than half the shell. Columella not much arcuated, whitish, rather abruptly truncated, connected with the upper extremity of the outer lip by a thin callosity. Length 81 millims., diam. 37 ; aperture 39 long, 20 wide. Hab. Between Zanzibar and Lake Tanganyika {Kirk). The granose surface of this species is the result of the coarse raised lines of growth being crossed by transverse impressed striae, which being somewhat remote from one another cause the granules to assume a rather elongate form. Mr. Alfred E. Craven informs me that the distinguished name of Dr. Kirk has already last year been associated with a species of this genus. Such being the case, I am compelled to alter the designation originally applied to this species ; and therefore I have much pleasure in substituting that of A. craveni. 16. ACHATINA THOMSONI. (Plate XXXIII. fig. 12.) Achatina thomsoni, E. A. Smith, Annals, loc. cit. Shell moderately solid, elongate ovate, beneath a yellow epidermis whitish, striped with blackish brown. Spire sometimes purplish red or whitish, more or less worn, and in consequence, to a certain extent, lacking the striping ; the latter is, as a rule, rather regular and only a little wavy. Whorls 7, a little convex, striated by the lines of growth, covered by a thin yellow epidermis, which is beautifully sculptured with most minute striae in a crisscross fashion, producing the woven appearance of a fabric; last whorl elongate, narrow, gradually descending. Aperture pyriform, bluish white. Columella arcuate, thickened, not very abruptly truncated at the base, united to the lip by a thin callosity. Length 75 millims., diam. 32; aperture 38 long, 21 broad. Hab. Between Lake Nyassa and east coast {Thomson). This species is remarkable for its narrow ovate form and the peculiar woven appearance of its epidermis. The proportion of the length of the aperture to that of the entire shell varies; in some specimens it occupies rather more than half the total length, and in others somewhat less. The deep-brown or black stripes edged with brown, as a rule, occupy more of the surface than the yellow spaces 19* |