TANAIDA. > & 
Tribe—VAGANTIA. 
THE non-parasitic aberrant crustacea are distinguished 
from the sub-parasitic ones not only by their different 
condition of life but also by their having fully developed 
gnathopoda (and consequently possessing seven pairs of 
legs), of which, at least, the anterior pair is of a large 
size and more or less cheliferous. 
They form two families, Tanaide and Anthuride. 
Fam.—TANAIDZ. 
Tue body in these Isopods is long and narrow. 
The head is confluent with the first segment of the 
body, the eyes are more or less distinctly placed on 
footstalks, The antennz vary in length. The first 
pair of gnathopoda, or the anterior pair of legs, are 
of large size and cheliferous, or terminated by a didac- 
tyle claw ; the second pair are of an intermediate form, 
but approximating more nearly to that of the pereiopoda 
than to that of the first pair. The eggs are borne 
in a sub-pectoral pouch beneath the five central segments 
of the body. The tail is terminated by two setaceous 
articulated appendages. 
The family corresponds with Professor Milne Edwards’ 
tribe of Asellotes hétéropodes—the Asellota heteropa of 
Latreille’s Familles naturelles. It comprises the genera 
Apseudes (Rhea), Tanais, Paratanais, and Leptochelia. 
The last-named exotic genus is especially interesting 
