MR. H. F. BLANFORD ON THE DESCRIBED FORMS OF TANALIA. 607 



more strongly marked (Fig. 3, T. Oardneri), the alternate ribs are more developed, 

 and those intervening narrow and filiform. In the next stages, the alternate ribs, or in 

 some specimens all the ribs, become undulated (Fig. 4), then nodular, the nodules being first 

 small and close (Fig. 5), and afterwards more distant and prominent (Fig. 6, T. loricata), 

 from which the passage into T. Skinnerl and T. erinacea consists in, first, some of the 

 spines, arid finally all, remaining unfilled and in the form of scales as they first appear at 

 th.e edge of the shell. The varieties T. airea, T. Layardi, T. Meevel, and T.funictilata 

 differ from T. Gardneri chiefly in the elevation of the spire and the greater and regular 

 development of the striae of growth. These forms (as has been remarked by Mr. Layard 

 in the case of the two first mentioned) pass into T. undnlata, and this again into T. 

 loricata, with an elevated spire. 



2. Colouring. 



When taken from the water, most specimens are more or less covered with adhering 

 Algae, which require soap and water and a stiif brush for their removal. When thus 

 cleaned, the epidermis is seen to be of a rich brown colour, varying from a pale yellow 

 brown to a tint bordering on black. Beneath this, the proper colouring of the shell is 

 always perceptible in young specimens, and frequently also in old. It is very clearly seen ■ 

 in the variety picta, which has a thin epidermis, and in which it assumes the form of 

 waved transverse bands varying in closeness and regularity, being sometimes so irregular 

 as to simulate a reticulate marbling. The variety T. Tennentii, from Ambegammoa, is 

 frequently marked in a similar manner. This is the commonest type of colouring in all 

 varieties ; the only modification of it I have observed is that in which the transverse 

 bands become more or less interrupted, but regularly(as in P. chilinoides), so as to form 

 spiral bands of zigzags. This is chiefly observable towards the aperture of full-grown 

 specimens, the young part of the shell having the normal colouring. I have met also 

 with a few cases in which the shell was colourless near the aperture. 



The painting of the peristome varies but little. The inner lip is coloured purplish, 

 brown ; and the tint sometimes extends round the outer lip also : it is the colour of the 

 callous deposit which strengthens the aperture of full-grown shells. Very frequently a 

 series of brown dots also ornaments the edge of the outer lip, being the tips of the zigzag 

 markings appearing beneath the callus. In old specimens this callus, the internal part 

 of which is white or brown, or white blotched with brown, extends far into the shell, 

 obscuring its zigzag markings. These remarks apply to all forms of Tanalia here 

 included under T. aculeata. 



3. T'orm of TVhorls, and Exsertion of the Spire. 



The form of the whorl varies but little throughout the species : it is always obliquely 

 flattened above, and in some specimens (var. dromedaria, e. g.) this feature is exaggerated 

 into a slight excavation of the whorl near the suture. The ribbed and nodulose varieties 

 differ in this respect as much as the smooth forms. The dilatation, or, in other words, the 

 ratio of increase in the growth, of the whorls varies also in aU varieties. The form of the 

 spu'e is very inconstant : it is sometimes as much exserted as in a typical Paludlna (e. g. 



VOIi. XXIII. 4 M 



