1236 



CRUSTACEA. 



these eyes was obtained with a magnifying power of two hundred 

 diameters ; yet sufficient to suggest that there were two lenses placed 

 side by side. See figs. 2 a, and 36, PI. 88. 



The anterior antennas are short, five- to seven-jointed, with scattered 

 setae seldom as long as the antenna. They project either side of the 

 head. 



The 'posterior antennae are slender prehensile, with a claw-shape 

 joint at apex, and not a tuft of setae. They are four-jointed, exclusive 

 of the claw, which is properly a fifth joint. The organ is flexed at 

 the second articulation, and the third and fourth joints are mostly in 

 a single line ; these two joints therefore constitute a kind of finger, 

 and are so designated for convenience in the following descriptions. 

 The second and fourth joints are the longest. The finger sometimes 

 is slightly longer than the second joint, and occasionally is less than 

 half as long. The claw is short, seldom when longest exceeding half 

 the finger in length. There is usually a very short seta on the inner 

 side of the second joint, near middle ; one or two at the apex of the 

 third joint, and often others at the apex of the fourth joint. 



The mouth (see figs. 4 d-l, Plate 88), consists of a pair of man- 

 dibles, without palpi; a first pair of short maxillae, having a few spines 

 at apex ; a second pair of maxillw, rather slender and corneous, some- 

 what furcate at apex, with one or two slender setose processes on the 

 under side, projecting when in position beneath and beyond the apex 

 of the maxilla, and another similar but shorter seta on the inner side. 

 The maxillipeds or the first pair of feet have a stout two- or three- 

 jointed base, and terminate in a corneous joint. In females, this cor- 

 neous joint is short and acute. In males, it is quite long, slender, and 

 bends around. Moreover, in male individuals, the large penult joint 

 of the base has a tuft of short setae on the inner side. It is evidently 

 used in grasping the female in coition. 



The natatories are eight in number, or four pairs. They are lamel- 

 lar, and the last pair is the smallest. 



The nervous system, in the species examined, contains a single, large 

 oblong ganglion, which embraces the oesophagus anteriorly (see fig. 2 a, 

 g, PI. 88). The pigment of the large eyes is often directly over the 

 anterior part of the ganglion ; the nerves passing to the eyes, or those ot 

 the first pair, were distinguished. One pair of nerves, from the anterior 

 margin of the ganglion, branches in the front portion of the head ; a 

 third pair, of large size, was seen going to the anterior antennas ; a 



