570 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvm. 



latter is much larg-er. In the fourth .swimming" legs the terminal joint 

 is longer, and the spines and setai ditfer slightly in their relative length 

 and arrang-ement. In both the male and female the bases of these 

 spines are reinforced by semicircular plates fringed with small hairs. 



Total length 4-5 mm. Length of carapace 2.35 mm; width of same 

 2 mm. ; length of g-enital seg-ment 0.75 mm. ; length of abdomen 1 mm. 



JV(iifj)lli(s larva. — Body elliptical, widest at about the center; width 

 to the length as 3 to 5. Appendages projecting far beyond the body 

 margin and typical in form (tig. 36, p. 536). 



First antennie uniramous, terminating' in two plumose seta^; second 

 antenna? and mandibles biramous; exopod four-jointed, endopod two- 

 jointed; each joint of exopod bearing a long plumose seta, while the 

 terminal joint of the endopod carries two seta?. 



The median eye is placed very far forward and concealed beneath a 

 spot of pigment. The anal sette are flattened spoon-shaped, of good 

 length, and they project sidewise from the l)ody instead of diagonally 

 backward. The color is a pale yellowish, with rust-colored pigment 

 distributed in five spots, a small area over the median eye anteriorly, 

 a large area on either side at the center, and a small area on either 

 side just in front of the anal sette or balancers. The pigment is com- 

 paratively faint and scarcely appears under a low power as it does in 

 other species. The anterior half of the body is very transparent and 

 shows the internal structure plainly. Total length, 0.4 mm. Width, 

 0.23 mm. 



Chalhimi^ stage. — Carapace elongate-ovate or spindle shape, nar- 

 rower anteriorly; frontal plates narrow and inclined backward along 

 the front margin of the carapace. Posterior lobes small, turned 

 inward strongly, and with scarcely any sinus; posterior margin of 

 carapace squarel}^ truncate. Eyes a little lieiiind the center of the 

 carapace, large and prominent; frontal gland very large and occup}^- 

 ing the whole of the anterior angle of the carapace. P>ee segment 

 much larger than in the adult, one-third the length, and more than 

 half the width of the carapace, its sides strongly convex. (Tenital 

 segment and a])domen at first fused and about the same width as the 

 free segment, but separating with the first moult, the abdomen several 

 times the larger. Anal lamin.e short and wide, and projecting diago- 

 nally sidewise rather than straight backward; the plumos'e setw verv 

 short and stout. Botii pairs of antenna? and all the mouth parts pres- 

 ent but somewhat rudimentary, especially the second antennae, whose 

 terminal joint is little more than a small spine on the tip of the large 

 basal joint (figs. 46-50). 



The first two pairs of swimming legs are the only ones developed in 

 early chalinuis stages, and they are worthy of notice from the fact 

 that the tirst pair is biraniose; but the endopod is made up- of a single 

 joint, which is very small and ([uickly disappears. Color the same as 



