140 
THE VOYAGE OF H.M.S. CHALLENGEE. 
Thalenessa digitata, n. sp. (PI. XXII. fig. 2 ; PI. XXIII. figs. 5, 6, 7 ; PI. XXV. 
figs. 4, 5 ; PI. XIIIa. figs. 7—10). 
Hahitat . — Dredged off the Admiralty Islands, March 1875 ; depth, 16 to 25 
fathoms. 
The specimen is in three fragments, the whole being about 125 mm. in length and 
about 5 mm. in breadth at the anterior third. 
The greater part of the body anteriorly is tinted dorsally of a brownish hue so as to 
relieve the pale scales. The colour fades anteriorly and posteriorly. 
The head (PI. XXII. fig. 2) is remarkably indistinct, being overlapped by the 
nuchal fold posteriorly ; and even when the latter is reflected, the ce23halic region is 
small. A pair of eyes of considerable size, and close together, occurs on each side. A 
short median tentacle lies in the centre anteriorly, with a short antenna close to the l3ase 
on each side. Each of these organs is shaped somewhat like an awl-handle with the 
smaller end free. Above the j)alpus is a double process, the base consisting of a stout 
pedicle with a lamellar frill along the inner border superiorly, and sj^litting midway 
into a smaller filiform superior tentacular cirrus, and a larger inferior one, which, however, 
hardly reaches the tip of the first pair of feet. The palpi are long and gently tapered 
from base to apex. 
Anteriorly the scales (PI. XXIII. fig. 7) are somewhat rounded, posteriorly 
irregularly reniform. Their surface is perfectly smooth. The external margin has a 
series of peculiar digitate papillae (PL XXV. fig. 5), the main stem being nearly 
cylindrical, then the process becomes bifid, and throughout the greater part of its length 
trifid, and some are provided with four digitations. Posteriorly one or two papillae are 
visible, and the processes on the margin are few, one or two only being trifid. The 
nerves passing to the papillose margin and other parts of the organ are well developed in 
both anterior and posterior scales. The latter present a more distinctly granular region 
in the neighbourhood of the digitate processes. In vertical (transverse) section both 
cuticle and hypoderm are fairly developed. The complexity of the muscles connected 
with the scale and papilla is great, the most varied motions of this organ being produced 
with ease. Thus, for instance, depression of the scale is effectively done by the vertical 
or slightly oblique muscles, while elevation is accomplished by the relaxation of these and 
the contraction of the transverse. 
The first pair of feet pass straight forward, and the second are directed only a little 
outward, so that the anterior margin (the palpi being curved backward inferiorly) 
appears to be formed of feet. The first foot (PI. XXV. fig. 4) bears a scale, and at the 
tip has a large translucent lamella projecting from the anterior (or, according to position, 
the inner) margin. The same process occurs at the extremity of the second foot, and in 
