714 MR. E. A. SMITH ON SHELLS FROM LAKE NYASSA. [NoV. 6, 



ber about sixteen in the last whorl ; the granules are produced by 

 transverse sulci, which cut the ribs at right angles ; they are squarish 

 and four or five in number on the ribs of the upper whorls, and the 

 same on the body-whorl, where they terminate about its middle, 

 beneath which the spiral ridges between tbe sulci are simple, and 

 rather finer than those at the upper part of the volution ; aperture 

 acuminately ovate, occupying rather more than one third of the en- 

 tire length of the shell. 



Length 18 millims., diam. 6g. 



This species must not be confounded with M. nodicincta, Dohrn, 

 also found at Lake Nyassa. Although in sculpture there is certainly 

 much resemblance, the very different form and proportion of the 

 whorls indicate the specific distinctness of this pretty shell. The 

 spire is produced to quite an acute apex ; and its outlines are recti- 

 linear. The nodules on the ribs are large for the size of the species, 

 squarish, and in oblique curves. The red dots are for the most part 

 situated in the interstices between the ribs, at the base of each 

 nodule, thus forming both longitudinal and transverse series. 



.5. Melania polymorpha. (Plate LXXV. figs. 4-10.) 



Shell elongate, pyramidal, thin, under a pale-olive epidermis, 

 whitish, sjiotted with reddish brown ; whorls 8-9, almost flat, some- 

 times somewhat convex, margined above at the suture, which is deep 

 and subcanaliculate, either with or without longitudinal plicae, nodu- 

 lous through being intersected by a few transverse striae ; the jilicae 

 are usually only on the upper whorls, but in some specimens there 

 are traces of them on the last, or they are well developed ; the body- 

 whorl is generally sculptured with 3-4 spiral sulci at the periphery, 

 and by other less distinct striae above and below it ; aperture ovate- 

 acuminate above, varying in length, occupying either a little more or 

 less than half the entire shell, pale horn- colour, spotted with 

 reddish brown. 



Length 16 millims., diam. .5|. Another specimen 14 milHms. 

 long, and A\ wide. 



The form of this species is subject to great variation ; and the ex- 

 tremes, taken apart from intermediate varieties, have decidedly the 

 aspect of distinct species. The sculpture is also very different in 

 certain specimens, some being almost smooth, with the exception of 

 the spiral sulci on the body- whorl, and a few less distinct striae on 

 this and the upper volutions. Others are distinctly ribbed, the ribs 

 being cut across by two spiral striae in the upper whorls, thus pro- 

 ducing three granules on each rib, the uppermost situated at the 

 suture on the thickened margin. This incrassation is constant in all 

 specimens ; and so is the deep suture, which gives the spire a tur- 

 reted aspect. Six small examples have the thickened margin very 

 strongly developed, the longitudinal ribs particularly granulous, and 

 present on the body-whorl, terminating at the periphery, where 

 they are limited by a few distinct spiral sulci. 



The disposition of the reddish-brown spotting and markings is 

 not constantly the same. Generally a series of dots, short, rounded, 



