ARCTURUS GRACILIS. 373 
ISOPODA,. ARCTURID. 
NORMALIA, 

ARCTURUS GRACILIS. 
Specific character. Very slender, quite smooth, and destitute of tubercles ; 
the upper antenne rather shorter than the first three joints of the lower; the 
fourth segment of the body linear-cylindric, and not tubercled. 
Length, seven lines. 
Leachia gracilis. H. Goopsrr, Edinb. New Phil. Journ. xxxi. p. 310, pl. 6, 
Arcturus gf. isa, Cat. Brit. Crust. p. 64. Pop. Hist. Brit. Crust. 
p. 222. 
In this species the body is very slender and quite 
smooth, without the tubercles, which are found in all 
the other species. The plate which covers the base of 
the antennz projects, and is rounded anteriorly. The 
superior antenna are almost as long as the first three 
joints of the inferior, the first joint being globular, the 
second and third linear, each as long as the first; the fla- 
gellum is equal in length, or longer, than the peduncle, 
and the last articulation is minute and linear. The 
inferior antennz are as long as the body, with the first 
joint obsolete, the second slightly clavate, and the flagel- 
lum strongly pectinated on their inferior edges. Both 
pairs of antenne have a few bristles scattered over them. 
The body is quite smooth, except a few scattered punc- 
tures. The fourth segment is linear, cylindrical, and not 
