220 OSCANIUS. 
Pleurobranchus blainvillii Less., Centurie Zoologique, p. 143, pl. 
51, f. 1 (1830); Voy autour du Monde, ete., La Coquille, Zool., ii, 
pt. 1, p. 291. 
O. MAMILLATUS Quoy & Gaimard. PI. 46, figs. 10, 14,15. 
Large, sometimes over 5 inches long, very soft, remarkable for 
the brilliance and pattern of colors, the long tubercles and the want 
of a shell. Mantle much undulating at the edges, notched in front, 
with a projection in the middle; surface bearing large conic tuber- 
cles, variegated with brown and yellow, the intervals colored with 
shades of reddish-brown and yellow, with spots of a beautiful brown ; 
and here and there are crescents of crimson lake, shaded with red- 
dish ; tentacles and head shield dark reddish-brown, the rest of the 
animal yellowish. Tentacles slit, united at the bases, where the eyes 
are situated, these being generally concealed by the front edge of 
dorsal shield. Below the tentacles is the wide, rounded veil, under 
which the short, large rostrum lies, at its termination the mouth, 
surrounded by rounded tubercles, bearing two membranous tessel- 
lated plates ; a short lingual ribbon in the angle formed by them. 
Foot wide, rounded, with a marginal groove in front, extending 
beyond the mantle behind. Gill free at the apex only, formed of 
alternating, very closely pinnate branches (fig. 14). Penis sur- 
rounded by palmate and jagged foliations. 
Port Louis, Mauritius. 
Pleurobranchus mamillatus Q. & G., Zool. Astrolabe, ii, p. 294, pl. 
22, f. 1-6: 
O. HILLI Hedley. PI. 47, figs. 18, 19. 
Animal elliptical, thick, subglobose ; in life, as well as I can re- 
collect, dark plum color; as contracted in alcohol measuring 140 
mill. in length by 120 mill. in width and 50 in height; without a 
shell. Mantle very large, thick and muscular, overlapping the body 
so as almost to envelope it; irregularly covered outside by numer- 
ous large, warty protuberances ; deeply, squarely notched in front, 
entire throughout the rest of its circumference. Rhinophores 
appressed to each other, externally split to the base, thick and sub- 
cylindrical. Eye not observed. Foot large, somewhat cordate in 
outline, bearing at the tail, on the sole and in the median line, a 
gland 30 mill. by 10 mill., distinguished from the rest of the sole by 
its thick transverse rugosities and black color. Gill-plume tucked 
in between the mantle and the foot, a third as long as the animal, 
