114 Memoirs of the Indian Museum. | Vor. VI, 
numbers to the neighbourhood of Colombo ; on the Indian side it reaches Manapad 
Point, somewhat south whereof it marches with the varieties globosa and comorinensis. 
It again appears on the shores of the Kathiawar Peninsula in considerable numbers. 
This variety is found in greatest profusion on sandy beds off Tuticorin at depths 
generally from 7 to 104 fathoms. It is also found in shallower water, but there it is 
not nearly so numerous as in deeper water and the shells are less vigorous and well 
grown. From these beds from 2 to 34 lakhs of shells are annually fished, with less 
than a quarter of a lakh from all the rest of the Gulf of Mannar ground. 
The typical var. acuta is comparatively narrow and moderately elongate with a 
well-balanced spiral ; the final whorl in mature shells shows no exaggerated inflation — 
as in the obtusa type and there is no marked angularity of shoulder, the position of 
which would be difficult to trace were it not for the presence of a well-marked row 
(the second) of periostracal nodes. On removal of the periostracum, vestigial 
inequalities are found, coinciding with the bold periostracal nodal eminences. The 
angular index of the spire ranges from 62° to 914°, with a mean of 778°. The 
breadth in the length averages 1°83 in medium-sized specimens of 6 inches length, 
reduced to 1°75 in the case of the largest and stoutest size (74 x 44 in.). Apart 
from the Kathiawar habitat, there are three well-marked local races :—(a) Tuticorin, 
(b) Kilakarai, and (c) Rameswaram. 
(a) The Tuticorin race.—Taking freedom of growth as shown by the well-balanced 
spiral of the whorls, neither unduly lax nor stunted into a squat coil, the massiveness 
of the shell, the-clean, strong development of the periostracum, the rapidity of 
growth, the large size attained both individually and on the average, and the great 
abundance in which they are found in spite of an annual thinning of their numbers 
that has run to an average of fully 250,000 during the past twenty centuries, the 
shells fished off Tuticorin and for about 30 miles north and south thereof, appear to 
represent the most vigorous strain of all. It may be taken as the typical local race 
of the central type of T'urbinella pirum. 
In representative shells the apical angle is low, averaging 77°8°, while the range 
in variation in this character, lying between 62° and 915°, is notably restricted, 
bespeaking a compact race living under uniform conditions. Periostracal growth is 
thick, bright olivaceous yellow in tint and obviously vigorously grown; the surface is 
normally clean and remarkably free from crusting growths, cleaner and brighter than 
in any other race I have seen. The development of the rows of periostracal nodes and 
nodules is correspondingly strongly marked. Usually there are six rows of nodules 
present, consisting of two shoulder rows, and four body rows. ‘The second or 
anterior shoulder row is the only one strongly developed. In a five-whorl shell, the 
number of nodules in this row are usually 3 to the inch; they vary somewhat and I 
have some shells whereon the nodes are specially large and coarse numbering only 
1°75 to the inch. The first shoulder row is usually present and well defined, but the 
nodules are generally less than half the size of those in the second row. Of the body 
rows, trace of all four series is nearly always present, but occasionally one is sup- 
pressed entirely—usually the fourth. They are not merely raised lines or ridges as 
