ORDER ISOPODA. 
219 
whose inferior antennae are always short, is distinguished 
from all the preceding by its strong and prominent mandibles. 
It is that of 
Synodus, Latr. 
In those which follow the tail is most frequently composed 
of but five segments. The length of the lower antenna) ex- 
ceeds the half of that of the body. 
Cirolana, Leach, 
Have six segments to the tail. 
Nelocira, Leach, 
Have but five, the cornea of the eye is smooth. 
Eurydice, Leach, 
Similar to Nelocira in the number of the caudal segments, 
remote from them in the character of their granular eyes. 
This subgenus conducts us to those in which these organs 
are formed of small grains, or simple eyes approximated, and 
which have besides the four antennae inserted on one and the 
same horizontal line, of four articulations at most, and all the 
feet ambulatory. The tail is composed of six segments, the 
last of which is large and suborbicular. Such are 
Limnoria, Leach. ( Limnoria Terebrans, Leach.) 
The third section, SPHA3ROMIDES, Latr., presents four 
very distinct antennae, setaceous or conical, and a single sub- 
genus excepted, (antlmra) always terminated by a stem, 
divided into many small and short articulations ; the lower 
always longer, are inserted beneath the under part of the first 
articulation of the upper, which is thick and broad. The 
mouth is composed as usual. The gills are vesicular or soft, 
naked, and disposed longitudinally in pairs. The tail pre- 
