460 PROCEEDINGS OF THE NATIONAL MUSEUM VoL. 113 
muscles are present. The ovaries form a rather thin layer on the 
inner side of the mantle-sac around the body. 
ee oily 
Figures 5-6.—Gorgonolaureus bikiniensis: 5, Filamentary appendage; 6, posterior part of 
body. Numerals denote the thoracic appendages. 
On the dorsal side of the prosoma, apparently connecting with 
the thorax, are a pair of large structureless filamentary appendages, 
corresponding to Brattstrém’s ‘‘horns.”’ 
Each filamentary appendage is directed posteriorly and gently 
bends upward within the mantle cavity filled with metanaupli. It is 
almost naked, but is scantily covered with fine hairs on the dorsal side 
and terminally (fig. 5). Contrary to previous authors’ views, these 
appendages, which are found also in other ascothoracids, may be 
looked upon as a structure concerned with respiration or the aeration 
of the mantle cavity for brooding, rather than as antennules or the 
first thoracic appendages. Apparently they may be homologous to 
such “horns” existing in some acrothoracids and ordinary pedunculate 
forms of the related Cirripedia. 
The thorax is apparently smaller than the head, but the segmenta- 
tion could not be well defined in situ because of the obscurity of the 
contents. At the posterior end the body abruptly narrows and bends 
ventrally (upwards, in situ), leading to the shortened abdomen. 
The abdomen protruded ventrally is very short and apparently 
unsegmented. Terminally it bears a pair of large caudal furca 
triangular in outline and fringed with fine hairs ventrally, and with 
longer hairs terminally. 
The first pair of the six thoracic appendages are slightly separated 
from the succeeding pairs, and the last are widely separated, lying 
close to the lateral sides of the abdomen. These legs are better 
