The Viviparous Water-Snail of lyake Biwa, Japan. 
401 
peripheral carina on the body- whorl and the region below it is entirely without 
spiral ridges. This region is relatively short and recedes abruptly below the peri- 
pheral keel m the body-whorl. The suture in vertical section is distinctly V-shaped. 
It is mode: ately oblique. The aperture is subcircular, sometimes subpentagonal 
owing to th peripheral keel forming a distinct angle on the outer lip and the upper 
extremity being truncate. The umbilicus is a mere chink or altogether closed. The 
whole shell is pale olivaceous green more or less densely clouded with black and 
with a dul) polish. The aperture when complete is narrowly edged with black and 
the interior is bluish white. The eroded apical region is chalky white. 
The ei ibrybnic shell differs from that of any other Viviparid with which I am 
acquaintedr It is rather broader than high and rather thick. There are 3^ whorls, 
the apical whorl and a half being very small. The obliquity of the suture increases 
rapidly so that the outer margin of the penultimate whorl is much deeper than the 
inner. The spiral ridges on the body-whorl are extremely broad and prominent. 
The minute sculpture consists of longitudinal striae and very fine transverse striae. 
The latter are not punctate. The aperture is relatively large and is produced above. 
The shell is of a very pale olive-green colour with the uppermost half-whorl brown- 
ish and the body-whorl sometimes irregularly streaked with black. 
Type-series No. 509 and M ^^^30 ^.S.I. (J. Anderson and N. Annandale coll.). 
Habitat. The species is apparently peculiar to Lake Biwa. It is a true lacustrine 
mollusc and occurs from the marginal region to a 
depth of over 300 feet. 
From that of L. sclateri (fig. 3), a species found 
in rice-fields round Lake Biwa, the adult shell is 
readily distinguished by its texture and sculpture 
and by the strictly conical outline of the upper 
region. The young shell is totally different in the 
two species, that of L. sclateri being normal and 
closely resembling that of other species of the genus 
Lecythoconcha.' The embryonic shell of H. turris 
perhaps resembles that of the Chinese genus Rivu- 
laria, Heude, but I can only judge of this by com- 
parison with adult shells of the latter. It bears a 
quite superficial resemblance to that of Margarya 
from Western China. 
The species of Viviparidae found round Lake 
Biwa in pools of water {malleata, Reeve) and in 
rice-fields {sclateri, Frauenfeld and japonica, V. Martens), I assign provisionally to 
my new genus Lecythoconcha. 
Fig. 3. — Large shell of Lecythoconcha 
sclateri (Fid.) (nat. size), from rice- 
field near L. Biwa. 
• For this group of species I have just proposed this new generic name, largely on anatomical grounds. The des- 
cription has been published in the Records of the Indian Museum, vol. XIX, p. iii (1920). 
