88 
PACIFIC SCIENCE, Vol. IV, April, 1950 
present, and a finely granulated shell sur- 
rounded the greater part of the larva (Fig. 
8k). 
From this time on, development proceeded 
rather slowly, no marked changes taking 
place until the free-swimming stage was 
reached, after 14 days of incubation. The 
velum consisted then of two circular lobes 
with a double line of purplish-pink around 
the borders. Eyes and otocysts were present. 
The foot terminated in a blunt translucent tip 
set with bristles. The operculum was observed 
in only one specimen and was small and 
rudimentary (Fig. 81, m) . The first whorl 
of the shell started with a corkscrew spiral 
as in the common snail. The apex was sprin- 
kled with granulations which tended to be 
in rows distally; while the distal half of the 
veliger shell was ornamented with granular 
spiral ridges. These ridges seemed to corre- 
spond to the transverse striae on the whorls 
of the adult shell. The shell was colorless 
and about 0.22 mm. long (Fig. 8 n—p). 
Mitra auriculoides Reeve 
Fig. 9 
On December 21, 1923, while collecting 
on the reef about 15 meters offshore near the 
laboratory, I found a group of egg cases at- 
tached to the undersurface of a rock, accom- 
panied by a Mitra auriculoides. There could 
hardly be any more doubt that the egg cases 
belonged to this mollusk than in the case of 
Mitra astricta obtained 2 years before under 
similar circumstances. Furthermore the com- 
parison of egg capsules, veliger larvae, and 
shells bore out this conclusion. 
The egg cases, about 100 in number, were 
crowded closely together and occupied nearly 
2 square cm. of the rock surface. The egg 
case, resembling greatly that of Mitra astricta, 
was club-shaped, about 4 mm. in length, and 
was attached to the rock at one end by a basal 
extension. The capsule wall was very thin 
and there were about 200 ova to the capsule. 
When the egg mass was found the capsules 
contained embryos in an advanced veliger 
stage, the coloring of which imparted a pale 
brownish tinge to the capsule (Fig. 9 a, b) . 
On December 28, the young escaped from 
their enclosures, and the close resemblance 
to both larva and shell of M. astricta was ob- 
vious. The same double band bordering the 
veliger Jobes was present, and the ridges and 
granulations on the shell were distributed as 
in the other species. The operculum, how- 
ever, showed a marked difference; while it 
was almost absent in M. astricta, it was well 
developed in this species. The foot was pro- 
FlG. 9. Mitra auriculoides Reeve, a, Egg cap- 
sules on rock; b, magnified capsule with embryos 
in veliger stage; c, d, free-swimming veliger; e, f, 
shell of free-swimming veliger. 
