CYCLOPOIDEA. ] Q23 



Legion I. LOPHYROPODA. 

 Tribe I. CYCLOPOIDEA. 



The Cyclopoidea have in general more the aspect of a Macroural 

 Crustacean, than any others of the Entomostraca. A few depressed 

 species look a little like Isopods, though without any other point of 

 special resemblance to that group. They are all minute, the largest 

 not exceeding one-third of an inch in length, and the size usually 

 varying between a twelfth and a twentieth of an inch. Figure 7, 

 Plate 70, represents one of the flattened species, a Sapphirina, and 

 figure 8, one that is slender and compressed, the two extremes, into 

 which the common type graduates. 



The cephalothorax is transversely articulated, and the shell of the 

 anterior segment never extends like a carapax over the following part 

 of the animal. 



The abdomen is extended in the same line with the thorax instead 

 of being inflexed, and bears at its extremity two lamellar or styliform 

 appendages. It is usually abruptly smaller than the thorax, as in 

 figure 5, but in some species, as in figures 7, 8, the two are regularly 

 continuous. 



Cephalothorax. — The cephalothorax consists ordinarily of but four 

 segments, one large anterior, and three short 'posterior (Plate 70, figs. 

 IB, Cyclops; 1 A, Calanus; 6, Corycceus; 7, Sapphirina). But the 

 number is often larger, being at times increased to seven. This 

 increase takes place in four ways : — 



1. By the addition of a fourth posterior segment to the extremity 

 of the thorax (Fig. 3, Calanus; 4, Eucheeta; 5, Pontella, Plate 70). 



2. By an articulation crossing the anterior segment, just anterior 

 to the mouth, separating a cephalic segment from the rest of the 

 cephalothorax, as in many Pontellw. 



3. By another articulation across the anterior segment posterior to 

 the mouth (b, fig. 5, Pontella), this articulation passing anterior to the 

 first pair of legs. 



4. By an articulation like the last-mentioned, but passing just ante- 

 rior to the second pair of legs, that is, the first pair of natatories (6, 

 fig. 2, Laophon). 



