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THE VOYAGE OF H.M.S. CHALLENGER. 
it passes between the tips of the oblique muscles. The pigmented granular hypodermic (?) 
area at the inner border of each ventral longitudinal muscle is also distinct. The 
ventral cuticle is very thick. The radiate fibres of the proboscis are coarser in texture 
and show the differentiation at each end formerly alluded to. The peritoneal 
corpuscles abound at the basis of the branchial processes, and on section are seen to 
pass out of the tip. In both this and the former the dorsal longitudinal muscles meet 
as a thin stratum over the dorsal arch. 
Thalenessa Jimbriata, n. sp. (PI. XIX. fig. 10 ; PI. XXIII. fig. 4 ; PI. XXIV. fig. 5; 
PI. XXV. figs. 1, 2 ; PL XIIIa. fig. 13). 
Habitat . — A single fragmentary specimen was dredged at Station 163b (off Port 
Jackson), June 3, 1874; lat. 33° 51' S., long. 151° 22' E. ; bottom temperature 63°'0, 
surface temperature 69° ‘0 ; depth, 30 to 35 fathoms ; sea-bottom, hard ground. 
A somewhat small form in fragments, measuring, in all, more than 30 mm., and 
with a transverse diameter of 4 mm., including the bristles. 
The head is covered by the first pair of scales and partly by the nuchal fold 
posteriorly. The eyes are formed on the same type as the preceding, and the pairs on 
each side are almost synophthalmic, and, moreover, the line of separation is nearly 
straight. The pigment of the anterior pair is somewhat triangular in outline, with 
the apex directed forward, and it is less dense than in the boldly marked posterior 
eyes. A short median tentacle alone remains, the small antennae probably having 
been removed in the dredge. The palpi are as long and finely tapered as in the fore- 
going species, and quite smooth. Their cuticle is very dense, and presents a closely 
arranged series of fine transverse lines. 
The first pair of scales are nearly circular, and perfectly smooth on surface 
and margin. The scales do not cover the dorsum anteriorly. They are marked by 
a nut-brown pigment along their anterior and posterior margins. Their external (or 
inferior) border has (PI. XXV. fig. 1) numerous fimbriate papillae, which, behind 
the anterior third of the bod}^, have often more than a dozen filiform divisions. A 
short and thick main stem (PI. XXV. fig. 2) springs from the border of the scale and 
soon breaks up dichotomously or irregularly into the filamentous processes, which have 
a different character from those of the preceding form. The scales are rounder 
in front, more or less reniform posteriorly. 
The dorsal branch of the foot (PI. XXIV. fig. 5) carries a series of somewhat short 
bristles, boldly spinous. In the anterior region of the body both this and the ventral 
division have numerous digitate papillae of considerable size. The inferior bristles in 
the same region present superiorly a few with double-jointed extremities, the rest 
