83 179 
dorsal margin, from which it is separated by a narrow groove which receives a 
corresponding tooth in the other valve. The internal ligament is small and is 
located just beneath the apices and behind the cardinal teeth in both the valves. 
The interior is dully pink. 
Long. 9 mm., alt. 85 mm., crass. 5 mm. 
Between Koh Mesan and Koh Chuen, 25—38 fathoms (*/2). 
Kellya rosea somewhat resembles K. rotunda, Desh., but is easily distinguished 
from it by its pink colour, and by the absence of the glossy iridescent surface of 
K. rotunda; neither is it so convex, and the valves are more gently and regularly 
rounded than in rotunda. For the rest, the species belonging to the genus Kellya 
vary considerably; not only do young and old individuals often differ greatly in 
form, but also full-grown specimens may often be very different in both form and 
outline. Young individuals of K. rosea (and also of other species) are usually longer 
in proportion to their height, and the ventral margin is straighter, than is the 
case in larger specimens. 
Kellya vitrina n. sp. 
(Pl. Ill, Figs. 21—22). 
This little species is hyaline, and somewhat silver-shining, thin, rather flat 
and triangular in form. The umbones are situated at about the middle of the 
longitudinal axis and the upper margin slopes gradually down on each side. The 
anterior and the posterior ends are rounded, the ventral side is fairly straight, and 
somewhat concave in the middle. The surface is smooth and ornamented with 
fine lines of growth; the concavity mentioned above extends from the ventral side 
upwards beyond the middle of the valves as a slight depression and disappears 
gradually towards the umbones. The interior of the valves is highly glossy, the 
hinge is composed of a single little posterior cardinal tooth in the right valve and 
two strong diverging teeth in the left, between which the internal ligament is 
situated. The right valve has, moreover, two long lateral lamellae, one on each 
side, parallel with and closely along its dorsal margin; and in the left valve is one 
solitary, very slightly developed lateral lamella directly upon the anterior dorsal 
margin. 
Long. 2°5 mm., alt. 2 mm., crass. 1 mm. 
Koh Chuen, 30 fathoms (1). 
In spite of its small size this characteristic species is undoubtedly full-grown; 
in outline it somewhat resembles Pylthina Deshayesiana, Hinds. 
Kellya elongata n. sp. 
(Pl. IM, Figs. 23—24). 
This species is oblong-ovate and convex, and opaque white in colour. The 
umbones which are situated towards the anterior end are slightly elevated above the 
hinge-line and terminate in obtuse, circular, glossy, shield-like bosses (the embryonic 
23° 
