1 882.] Representing the order Phyllocarida. Z67 



to the abdominal feet, we find that they are simple, without gills, 

 and entirely different from the leaf-like thoracic appendages, and 

 we have in this differentiation of true abdominal from the thoracic 

 feet a Malacostracan character, one quite unlike the differentia- 

 tion or blending of the two regions in the Phyllopods. 



The abdomen is nine-jointed, the segments cylindrical and 

 edged with obtuse spines (PL xm, Fig. 8) much as in Copepoda. 

 In their general form the abdominal legs appear to resemble 

 the simple biramous legs of the Copepoda, but still more closely 

 those of the Amphipoda, in which, as Claus observes, there is a 

 similar retinaculum. (See also Milne-Edwards's Crustacea, PI. 30, 

 Fig. 3".) 



The 5th and 6th segments of the abdomen bear much smaller, 

 more rudimentary legs. The 1st pair (PI. xiv, Fig. 5) are seen to 

 be two-jointed, the 2d joint long and slender, bearing near the 

 end stout raptorial setae, and on the inner edge slender setae. The 

 6th pair are still more rudimentary, one-jointed, and with but few 

 setae, which are stiff and coarse. These resemble the simple un- 

 branched 5th and last pair of abdominal feet in Copepoda (Ca- 

 lanus $). 



The long, slender terminal segment: bears two very long, nar- 

 row cercopods (PI. xm, Fig. 7; ending in one large and several 

 small setae, but there is no telson ; the cercopods are simple, the 

 integument entirely smooth, with no striae or any other markings, 

 and they are edged externally with short, and internally with long 

 ciliated setae. In the absence of a telson Nebalia differs from 

 Cuma or any other Decapod, and in this respect, and the simple 

 cercopods, shows a close resemblance to the terminal segment 

 with its two setiferous cercopods of the Copepoda. 



Internal anatomy. — Claus remarks in his " Untersuchungen zur 

 Erforschung der genealogischen Grundlage des Crustacean-Sys- 

 tems" (1876), that in all the internal systems of organs, Nebalia 

 is considerably removed from the Phyllopoda, and shows an im- 

 mediate relationship to the Malacostraca, sometimes approaching 

 near the Amphipoda, sometimes near the Mysidae. The ner- 

 vous system consists of a large two-lobed brain and of a ventral 

 cord extending through all the limb-bearing segments, there be- 

 ing, as shown in Metschnikoff's Fig. 25 of the embryo, seventeen 

 ganglia, corresponding to the seventeen limb-bearing segments of 

 the body behind the head. A transverse section of a ventral 



