As regards the general shape of the body, in the greater number of the 

 forms it is very slender and more or less cylindrical, with no very pronounced demar- 

 cation between the anterior and posterior divisions. In some cases, however, the 

 posterior division, including the last segment of the metasome, appears abruptly 

 much narrower than the anterior, which may be more or less expanded, as in 

 the Cyclopoida, for instance, in the genera Misophria, Pseudotachidius, Idya, etc. 

 In some forms both the anterior and posterior divisions appear greatly expanded, 

 whereby the body acquires a pronouncedly depressed, even leaf-like form, as in 

 the genera Zaus, Peltidium, Porcellidium. In other cases, quite contrary to this, 

 the body is found to be highly compressed, for instance in the genus Amymone. 



The cephalosome is generally coalesced with the 1st segment of the meta- 

 some, though in some few forms a well-marked demarcation between them may 

 be found to exist. The lateral parts of this section are more or less expanded, 

 being so deep in some forms, e. g. the genus Longipedia, that they wholly include 

 between them the oral appendages. It projects in front in a more or less distinct, 

 generally lamellar rostrum, which in most cases is movably connected with the 

 cephalic shield. The 3 succeeding segments of the metasome are always well 

 defined, and are provided with more or less distinct epimeral plates. The last 

 segment of the metasome, as stated above, has always a very movable articulation 

 with the preceding segment, whereas it is firmly connected with the 1st segment 

 of the urosome. Its epimeral plates are generally obsolete, or at any rate much 

 smaller than on the preceding segments. The urosome is composed of 5 segments, 

 the first 2 of which, however, in the female are more or less completely coalesced, 

 though in some forms a distinct suture between them is seen dorsally. In the 

 male these 2 segments are always distinctly separated, and the 1st of them pro- 

 jects at the end, on each side of the ventral face, to a small setiferous process. 

 The caudal rami are in most cases short, and firmly connected with the last 

 caudal segment. Of the apical setse, as a rule, only the 2 middle ones are well 

 developed, the others being more or less rudimentary. A single eye is generally 

 present, though in some forms, especially in those from deep water, no trace of 

 such an organ is to be found. 



The anterior antennae are, as a rule, @f inferior size and composed 

 of a limited number of articulations, rarely (as in the genus Misophria) ex- 

 ceeding 8 in all. One of the articulations, generally the 3rd or 4th, exhibits 

 at the end anteriorly a projecting knob, to which a slender sensory appen- 

 dage is attached, and the succeeding portion of the antenna is generally 

 abruptly narrowed, forming a well-defined terminal part. In the male both these 

 antenna? are prehensile, and often greatly swollen in their outer part. The 



