338 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXXIII. 



rower. The second free, which is reall}" the fourth thoracic, segment 

 is jnst lialf as wide as tlie first, wnth strongly convex sides. 



The last segment, wliich 



'^^" 



is a fusion of the genital 

 segment and abdomen, has 

 the same width as the 

 fourth thorax segment, but 

 is three times as long and 

 somewhat narrowed pos- 

 teriorly. 



The anal laminae are 

 relatively larger than in 

 Alehion, but are tipped 

 with much shorter setae, 

 five on each lamina. 



The first antennae are 

 two-jointed, the terminal 

 joint short and armed with 

 small spines only, with- 

 out the plumose setiB found in both the Caliginae and the Eurypho- 

 rina?. The second antennae are similar to those of Alehion, but with 

 two stout accessory spines on the inner margin near the base. 



Fig. 7.— The mouth tube, maxilla, and mandibles of 



THE METANAUPLIUS OF NeSIPPUS ALATUS. 



IX--^^ 



Fig. 8.- 



-A MANDIBLE OF THE METANAUPLIUS OF 

 NeSIPPUS ALATUS. 



The proboscis is also similar to that 

 of Alehion, but is longer and of a more 

 uniform width tlu"oughout (fig. 7). At 

 its tip can be seen the mandibles, which 

 are slender, somewhat enlarged, curved 

 toward the free ends, and coarsely 

 toothed along the inner concave mar- 

 gins. At this stage only the tips of the 

 mandibles touch each other. Later, 

 when the end of the mouth tube is com- 

 pressed laterally, the entire toothed 

 portion is interlocked (fig. 8). 



The second maxillae are close to the 

 base of the mouth tube on either side, 

 are simple, and consist of a stout conical 

 base tipped with a short and stragiht 

 spine. On the outer side of the base is another shorter spine, repre- 

 senting the rudimentary exopod ; this rudiment is seemingly lost in 

 later development. The first maxillipeds are slender and two-jointed, 



Fig. 9.— The first and second max- 

 illipeds OF the METANAUPLIUS OF 

 NeSIPPUS ALATUS. 



