TDOTEA. 377 



the tip. At the base of each of the foot-jaws is attached 

 a large movable sub-oval plate. The mandibles are 

 robust, with a strong, curved, denticulated apical blade, 

 below which is a small movable plate, and a broad 

 truncated molar tubercle : they are destitute of an arti- 

 culated palpiform appendage. 



The outer maxillae are very delicate, and terminated 

 by three oblong strongly ciliated plates ; the inner max- 

 illae have an elongated base and two thin terminal lobes 

 of unequal size, ciliated at the tips : the lower lip is 

 thin, with a deep incision in the middle of its anterior 

 margin (fig. * in page 379). 



The legs are all formed for walking, rather than for 

 prehension or swimming; they are nearly of uniform 

 structure, the anterior pair being not larger than the 

 following ; they, however, increase gradually in length to 

 the hind pair. In the female, the third and three follow- 

 ing pairs of legs bear at the base of each a large mem- 

 branous plate, folded beneath the body, forming a large 

 ovigerous sac. The tail consists of a very large terminal 

 flattened shield, preceded by three very short segments, of 

 which the third is dorsally fused with the next succeeding. 

 In /. Entomon, a Baltic species, there are three distinct and 

 two apparent joints in this part of the body ; in other 

 species, the soldering together more or less completely of 

 two or more of the short basal joints takes place, until in 

 /. appendiculata the tail appears to consist of only a single 

 large plate-like shield, traces of the articulations being 

 only visible at the lateral margins of the basal portion of 

 the joint.* The normal six-jointed structure of the tail 

 is, on the contrary, proved on the ventral surface of the 



* The variations in the condition of these basal segments have furnished 

 Professor Milne Edwards with the characters for distributing the species into 

 various minor groups. 



