MOLLUSCA OF INDIA. 187 
In the species of which I have been enabled to examine a series, I 
find that the perfect tube is invariably of uniform length in each 
form. ‘The character is so important, that 1 have thought it worthy 
of notice in the sectional arrangement.’ I can bear this out ; hun- 
dreds of specimens may be taken of any one species, and the tube is 
invariably of the same length and form. 
The above arrangement was a great advance towards a better 
knowledge of the genus ; but in 1859 only about 20 species had been 
discovered, and as they began to multiply it was soon evident that 
the above three sections could not be so distinctly separated by any 
hard-and-fast line, and Sections 1 and 2 were soon blended. 
In a little over 54 years (1864) the number of species had mounted 
up to about 37, 31 being from the Indian area. And in this year 
Mr. W. T. Blanford published his most excellent paper in the 
‘Annals and Magazine of Natural History, “On the Classification 
of the Cyclostomacea of Eastern Asia,” and which must form the 
basis and starting-point of all future classification of the group; he 
arranged all the then known species in eight typical groups including 
Dioryx. Owing to the above author’s subsequent observations, added 
to the valuable work done by Stoliczka in the same field, this requires 
to be somewhat modified. Many more species have been since dis- 
covered. ‘Theobald’s Supplementary Catalogue enumerates 56 (ex- 
cluding A. makarse, G.-A., MS., never described), and 10 more, in- 
cluding those now described in this part, bring the number up to 66 
that are known to me; while numerous species have been found 
in Siam, the Malay Archipelago, and several new species yet remain 
in my own collection. 
If we take the more important characters of this very remarkable 
well-defined genus—such as: (1) the sutural tube; (2) form of the 
aperture, circular, angular, or crenulated, with varying peristome ; 
(3) form of the constriction (most varied); (4) whorls, regular, 
compressed, more or less closely wound; (5) sculpture of whorls 
above and that adjacent to sutural tube ; (6) operculum ; and, lastly, 
the general form of the shell—we find Nature manipulates the above 
in every conceivable way with Geographical Distribution, and it 
becomes almost impossible to restrict a group by any very fixed boun- 
daries, forms merging most beautifully one into the other; I shall 
not attempt, therefore, any fresh arrangement until many more 
have been figured. 
Dioryx, restricted to such forms as amphora, urnula, &e., is one 
of the most distinct subdivisions that can be retained. The points 
of difference are its smooth globose form, position of constriction 
and operculum, and the long sutural tube. 
Another well-marked section quite as worthy of subgeneric 
distinction is type li. of Blanford ; it would contain all those species 
like constrictus, Bs., and may be thus described :—Shell perforated, 
ovately conical; sculpture consisting of very fine, regular, close 
ribbing on the inflated portion of the shell; sutural tube very 
short, clubbed or pear-shaped. 
The small size of the figures illustrating this genus in the ¢ Con- 
