NOTAEOLIDIA. 21 
irregular intervals. In all there are about ninety on each side. They are 
somewhat wrinkled, and this rugose appearance is increased by their bearing 
a little white pigment, arranged in irregular lines. In front the  side-flaps 
turn inwards, so that the cerata stand in front of the rhinophores; but they 
are set distinctly on the flap, and not on the head. Behind, the cerata of the 
two sides meet at the tip of the tail, the free portion of which is very small and 
hardly 1 mm. long. The dorsal margin and cerata are irregularly undulated. 
There is no frontal veil, but the region in front of the rhinophores passes 
directly into two very thick, conical, oral tentacles, 6°5 mm. long, and 5 broad at 
the base. Between them lies the mouth, which seems small and circular, but is 
much contracted. The anterior margin of the foot is grooved, and perhaps notched ; 
but this character could not be ascertained with certainty, owing to contraction. 
The foot is folded inwards, but in a natural condition must have had wide, expanded 
margins, and have been about 10 mm. broad. The rhinophores, which are set close 
together, are about 4°5 mm. high, and bear fifteen distinct perfoliations. At the 
base are folds of skin, but not regular pits. The genital orifices are 13 mm., and 
Fie, 22.—Notaeolidia depressa—RHACHIDIAN Fic, 23.—Notaeolidia depressa—RHAcHIDIAN TooTH 
TOOTH FROM ABOVE. FROM THE SIDE. 
the vent 20 mm. from the head. The former are small, and not surrounded by 
large folds of skin; the latter is an elongate papilla, half way down the side. 
The pericardium is not prominent. 
The internal organs are poorly preserved, but appear to resemble those of 
N. gigas in their essential features. The central nervous system is small, the eyes 
black and minute. No salivary glands were discovered, but they probably exist. 
The jaws are thin, with a smooth edge. The formula of the radula is 20 x 4.1.4, 
and the teeth are much as in UN. gigas, but the central tooth (figs. 22 and 23) is not 
so square, and has sloping sides. It has a rather lower median cusp with eight to nine 
strong denticles, but is not striated. The laterals are higher and narrower, with deeper 
and more distinct denticulations. Even the outermost lateral has about twelve fine 
but clear denticulations. The cesophagus is short, the stomach large, strongly 
laminated, and constricted in the middle. The liver is folliculate, and arranged much 
as in NV. gigas. The main trunk gives off six branches on each side, which form a 
layer of ramifications in the mantle margin and sides of the dorsal area, from. which 
diverticula pass into the cerata. The space filled by this layer is considerably 
