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 



SynoduSj Latr. 



In those which follow the tail is most frequently composed 

 of but five segments. The length of the lower antennae 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. 



EuRYDiCEj 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, SpHiE ROM ides, Latr., presents four 

 very distinct antennae, setaceous or conical, and a single sub- 

 genus excepted, (anthura) 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- 



