246 



Records of the Indian Museum. [Vol. XXII, 



periphery of the body-whorl is often surrounded by a line of ex- 

 tremely fine hairs representing degenerate chaetae. In the Siamese 

 V. ciliata (Reeve),' in which a larger number of secondary peri- 

 ostracal ridges probably bear chaetae than in V. dissiniilis, they 

 persist throughout life on all the whorls of the shell, and in some 

 individuals of the Chinese V. lapillorum (Heude) ^ they are coarsely 

 developed on the peripheral keel of the bodj'-whorl. 



In species of Vivipara such as V. bengalensis, in which the 

 embryonic shell is extremely thin and fragile, it is difficult to 

 demonstrate the existence of any true test-sculpture as distinct 

 from that of the periostracum, but by means of careful manipula- 

 tion of lighting under a binocular microscope it can be seen that 

 each of the rows of chaetae is situated on a slight elevation. This 

 can be more readily demonstrated in such forms as L. lecythis (fig. 

 II), in which the test is much thicker at birth ; while the chaetifer- 



I'lG. II. — Embryonic shell of Lecythoconcha lecytliis (Branson). 



A. Lateral view of the whole shell at birth (magnified). 



B. Protoconch as seen from above (more highly magnified). 



ous ridges are conspicuous from the first in certain other species, 

 such as Margarya inelanoides^^ Tata intha * and the peculiar Japanese 

 Heterogen tnrris} In these three species they are comparatively 

 broad and blunt. In V. dissimils and V. oxytropis, although the 

 embryonic shell is no thicker than in V . bengalensis, they are more 

 prominent than in that species, but thin and sharp. Generally 

 speaking, a strong development of the three primar}- ridges in the 

 embryonic shell is correlated with a coarse and well-developed spiral 

 sculpture in that of the adult, but this is not so in Heterogen, in 

 which it becomes graduallj' much less conspicuous on the younger 

 whorls. In H. iiirris, however, the only species of the genus 

 known, as in the African Xeothauina, Smith, and in many species 



' Reeve, Conch. Icon. XI\' (Paludhia), pi. vi, fig. ,:;6 (1S64). 



- Annandale, Mem. As. Soc. Bengal \'\, p. 314, pi. x, fig. 9 (igiS). 



■'' Kobelt on Vivipai-a, in new edit, of Mart, and Chemn., Conch. Cab., pi. 

 •vxxvii, xxxviii ClQoqj. 

 ' , ■• .\nnandale, Rec.Ind. Mtis. XIV, pi. xvii, fig. 7; pi. xviii, fig. lo(igi8i. 



' Annandale, Mem. As. Soc. Bengal VI, p. 4.00, figs, i 2. (1921I. 



