OSCANIUS. 219 
culated at their bases. The gill is attached two-thirds of its length 
by a lax thin membrane. Anal duct at the posterior end of the 
membrane, it is cylindrical, truncate and deeply crenulate at the tip. 
Generative organs very large, immediately anterior to the gill, con- 
nected by a prominent grooved ridge. Whole upper surface of the 
mantle covered with a reticulation of pale bluish ash lines, inter- 
_ spaces fawn color, becoming obsolete toward the margin and more or 
less dotted with whitish. Also ornamented with a large oblong 
dorsal spot of deep purple-brown, and a series of irregular shaped 
spots surrounding it, of same color, all of which are dotted with pale- 
blue. Head pale, mottled with purple-brown. Tentacles pale at 
their tips and lineated transversely with darker. The inner portion 
of the under side of the mantle and upper side of the foot deep 
purple-brown. Locomotive disk bluish-ash, tinged anteriorly with 
cream-yellow, and marked posteriorly with a purple-brown stripe. 
Veil same color as foot. Gill deep purple-brown, generative organs 
purple-black. Length six inches. (Pse.). 
Huahine. 
Pleurobranchus grandis Psx., Amer. Journ. Conch., iv, p. 78, pl. 
10, f. 2 (1868). 
This large and delicate species differs from others of the genus, in 
the mantle being extended over the head and notched for the accom- 
modation of the tentacles ; also in the attachment of the branchial 
plume to the body and the plumules being tuberculated at their 
base, for reason probably of the large size of the gill. After close 
examination of several specimens no shell was found. (Pse.). 
Closely allied to the next species. 
O. BLAINVILLII Lesson. PI. 49, fig. 42. 
Length nearly 33 inches, alt. 24 inches. Dorsal disk thin, flat, 
fleshy and oval, rounded behind, having a sinus in front; of the 
bluish-white color of porcelain, with white strize and some purplish 
rays in the middle; ochrey red toward the anterior border; buccal 
tentacles and generative organs purple-black. Gill an elegant, bi- 
pinnate plume of purplish color. Violet rose tints the body and is 
grooved by ramifying bluish strie. The foot is flat, smooth, bluish- 
white, thicker and colored with carmine at the edge; it is rounded 
in front and terminates in an obtuse point posteriorly. 
Point Venus, Bay of Matavai, Tahiti (Lesson). 
