OF SOUTHERN INDIA. 429 
to it the fossil Acteonella. Some time ago I have suggested for the last named 
genus the name Volvulina, but as Meek’s* proposition of the change in the generic 
names has priority I have adopted it here, though it would have been decidedly 
preferable to retain the name Act@onella for the species of the type A. gigantea, 
which was described and figured by d’Orbigny before the other species. As, 
however, the publication of all the species bears the same date, it of course 
rests with subsequent authors to retain any of those described as the type of the 
genus. 
b. Sub-family,—BULLIN A. 
Shell convolute, ventricose, more or less covered by the lateral edges of the 
foot, aperture enlarged anteriorly and roundish, inner lip anteriorly sometimes 
conspicuously twisted. 
The animal has the left side of the mantle generally more developed and 
thicker than the right one; the tentacles are at their bases united with the 
head-disk, but posteriorly they are generally distinct ; the dentition consists of one 
squarish central tooth, and numerous similarly formed lateral ones; the following 
genera have to be placed in this sub-family ; 
6. Bulla, Klein, 1857 (H. and A. Adams, Gen. II, p. 15). 
7. Haminea, Leach, 1847 (ibid., p. 16). 
8. Atys, Montfort, 1810 (<bid., p. 20). 
The shell of Bulla is thick and usually mottled on the surface, that of 
Haminea thin with distinct striz of growth, and Atys is generally spirally sulcated 
towards the anterior and posterior ends of the shell, which is rather solid, but 
transparent. 
The thickness and the transparency of the shells of the Buxzzmzt vary from 
different causes. The truly marine and littoral species usually have it solid and 
thick, those living in brackish water like Haminea, thin and fragile, being more 
horny and covered with an epidermis; those living in deep water or in the high 
sea usually have a thin but compact and somewhat elastic shell, being, as a rule, 
without an epidermis. 
Of the genus dtys H. and A. Adams quote two sub-genera, Dinia and Sao. 
In the former the inner lip terminates anteriorly with a dentiform plate; the latter 
mostly includes pyriform species, being gibbose anteriorly and usually umbilicated ; 
the columella is reflexed, but not truncated. A. Adams says in Ann. mag. nat. hist., 
1861, VIII, p. 189, that some of the species of Sao have been described under 
Cylichna, but that they neither belong to that genus nor to Atys, but have to be 
distinguished as a separate genus. In the next year (ibid., IX, p. 158) the same 
author, in describing a number of new species of Atys from the Japan sea, sub-divides 
* American Journal, XXXV, p. 93. On account of the great delay we usually have to endure in 
receiving American books, I only became acquainted with this paper last year, after the publication of the 
first part of our Gastropoda. 
7 As also of other Gastropoda. 
