II8 Memoirs of the Indian Museum. Vor 
some special characteristics, one morphological, the other physical. The former lies 
in the peculiar way in which the uncovered portion of each whorl has a straight 
profile between the bounding sutures, whereas in var. acuta the profile of the exposed 
part of each whorl is more or less convex. The profile of the two forms may be 
represented diagrammatically as shown in text-fig. 3. 
In comorinensis the edge of each succeeding whorl projects slightly beyond the 
one preceding, thus forming a slight collar; in acuta the edge does not so project. 
The physical difference of this form from others is its brittleness and comparative 
thinness. This renders it difficult to cut, as even a slight blow suffices to fracture it. 
The periostracum is inclined to be smooth, with weakly developed nodal lines. The 
first row is normally absent, as are also the body rows as a rule. The shoulder row 
alone is usually present, but with nodes very weakly developed. In some itis practi- 
cally absent. In colour this variety is remarkable for its extreme whiteness, a point 
in its favour with bangle-makers, but much discounted by its fragility. It grows to 
a fair size, but is always light and comparatively thin. 
Like some of the shells of var. obtusa fished in the shallows of the S.W. corner of 
Palk Bay, a proportion of the present variety show the spire much worn down by 
attrition. 
4. Variety globosa, var. nov. 
The range of this variety coincides geographically with comorinensis, but it lives 
at a greater depth—comorinensis being essentially an inshore form. Globosa exhibits 
extreme inflation of the body whorl, an apex of abbreviated acuta form, a dense, 
coatse periostracum ornamented with more than usually prominent lines and nodal 
eminences, a heavy and thick shell, and a red tinge within the mouth. Its length 
compared with the diameter is markedly short, the diameter ranging between 1°5 to 
17 in the length. Two typical forms measure respectively 6 x 34 inches and 5 x 34 
inches. The apical angle ranges between 80° and 110°, with a mean of 92°. The 
largest shells show very strong development of all the nodular rows, but whereas in 
the Turicorin shells of var. acuta the second shoulder row is normally conspicuously 
better defined than the others, in globosa the pre-eminence of this particular row 
tends to disappear and the tendency here is towards equality of the nodes in all the 
rows. There is usually scarcely any greater prominence of the shoulder nodes over 
those of the first row or those of the second upper body rows; of the latter there are 
usually four present (Pl. XI, fig. g—the lower five shells). 
5. Variety fusus, Sowerby. 
This is confined to the Andaman Islands. In general form it differs from the 
continental varieties mainly in the shape of the shoulder portion of the whorls. In . 
the Andaman individuals this is strongly marked in medium-sized individuals and 
distinctively angular; it is further emphasized by the great prominence of the shoul- _ 
der row of periostracal nodes which are more protuberant than in any of the other 
— | us à ns 
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