155 
tends anteriorly and upwards about half way to the anterior 
margin of the segment. The inferior and posterior margins of 
the first to fifth segments of pleon (inclusive) are regularly fringed 
with long setae, thickly set on the inferior margin but more sparsely 
placed on the posterior margin. On the inferior margin of the 
sixth segment the corresponding setae (about 15 or 16 in number) 
are short and stout, almost spiniform, most of them bear 4 or 5 
pectinations on the posterior edge toward the end of the setae. 
The projections at the end of the tail piece are thickly covered 
with Setae of various sizes, some of them thick and spiniform. 
Surface of body .- -In the pereion the surface has a crinkled 
appearance caused by numerous shallow depressions separated by 
small narrow ridges ; the first segment is smoother than the others 
and the surface of the head is also smooth. The surface of the 
pleon with the exception, to some extent, of the dorsal surface is 
smooth. In the pereion there are a few setae partially arranged 
in tufts scattered about on the dorsal surface, and the inferior 
angles both of the segments and of the epimera usually bear a few 
short setae. In the pleon, especially in the posterior segments, 
the dorsal surface is covered with a thick fur of short setae with 
some longer scattered setae as in the pereion, but more numerous. 
The long setae on the margins of the segments of the pleon have 
been already mentioned 
The ground tint of the colour is a light brown and is seen in 
the appendages, but in the body this ground tint is almost covered 
with marbled markings of a much darker brown, the lighter colour 
showing up in more or less rounded patches on the head and here 
and there on the segments of the pereion. The lateral portions of 
the pleon are usually darker than the other parts of the body and 
of a uniform slaty colour. This colour is probably protective — 
Mr. Helms notes that the animals looked exceedingly like the 
surrounding earth. 
Upper antenna. (Plate xxiii., fig. 2.) — The upper antenna is 
short, scarcely reaching to the end of the peduncle of the lower 
antenna, the peduncle apparently consists of three joints, but is not 
clearly distinguishable from the flagellum. The first joint is 
partially hidden by the head, it is longer and broader than the 
second joint, which is of about the same length as the third, but 
broader. The flagellum consists of from 5 to 7 joints, the proximal 
joints usually short, the others longer and swollen, this being most 
noticeable in the third and fourth joints from the end; the terminal 
joint is very small and is tipped with a few setae. The swelling 
of the terminal joints is chiefly confined to the chitinous integu- 
ment, the central portion containing the muscles &c. not being 
similarly swollen. The setae on the antenna are few and small ; 
there are a few on the second and third joints of the peduncle 
and on some of the joints of the flagellum. On the last four joints 
