OPTSTHOBEANCHIATA FROM THE ABKOLHOS ISLANDS. 571 
Species Splanchnotrophus saccolatds, sp. nov. (PI. 30. figs. 65, 66.) 
Female. Tlie body is elongated and roughly cylindrical, but slightly 
depressed dorso-ventrally, and it is encased in a thin, not very strong, 
layer of semi-transparent chitin. It is composed of a cephalothorax, of 
wliich tlie anterior portion is the head, but it' is not distinctly marked off 
from the thorax, and a much smaller abdomerj. On the dorsal surface of the 
cephalothorax are three sac-like outbulgings of the body-wall. The first of 
these is in the form of a transverse collar-like ridge right across the body, 
and it is somewhat firmer than the other two. Tlie second is much larger, 
more inflated, and more irregular. The anterior border and the latei'al lobes 
of it are sharply marked off from the body, but in the mid-dorsal region the 
liinder parts of the two lateral lobes merge with the general surface of the 
body. The third sac is, if anything, larger than tlie second, and its lateral 
lobes show a slight marginal indentation. 
The last portion of the thorax is narrower than that in front, but it swells 
out towards its hinder edge and then rapidly narrows again still further to 
• the point wiiere it joins the abdomen. 
From the ventro-lateral aspects of the cephalothorax arise three pairs of 
long, tapering, cylindrical outgrowths. The first pair arise at a level between 
the first and second dorsal sacs. The second pair arise at a level between the 
second and third dorsal sacs, and the third pair touch the second and are 
level with the third dorsal sac. These lateral outgrowths are not, as might 
be supposed at first sight, modified appendages, for the rudiments of these lie 
on the ventral surface, but the}' are outgrowths of the body-wall. They are 
very conspicuous, as they almost double the length of the animal itself, and 
apparently are concerned with the absorption of nutritive material from the 
host, since they lie in the spaces between the viscera. 
Strings of eggs, either in single or double rows, show through the body- 
wall and form a network of interlacing lines in the various parts of the 
ce[)halothorax, the dorsal sacs, and the basal portions of the long outgrowths. 
The first antenna3 are a pair of minute, stumpy, seemingly uniramous 
appendages lying under the head a short distance from the anterior end. 
Each is apparently composed of three joints and bears a number of relatively 
stout spines ; there are three of these on the basal joint, two on the next, and 
two on the terminal joint. The second antennae, while still small, are con- 
siderably larger than the first, and are plump, fleshy, uniramous appendages 
also showing indications of three joints. They are relatively shorter than the 
corresponding members in S. gracilis. Stout spines are also present on 
these : two on the basal joint, one on the next, and two on the terminal 
joint. 
The labrum is large, curved ventrally, and sub-triangular in shape with a 
rounded apex and a deep curved indentation in the base. The mouth pre- 
sumably lies under this indentation. The mandibles are small and consist of 
