592 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvm. 



irregular marginal band. And often the pigment extends out into the 

 antennules almost to their distal end and into the basipods of the other 

 two pairs of appendages. The balancers on either side of the anus 

 are long and stout (0.12 by 0.01 mm.), their length exceeding that of 

 the anterior appendages, exclusive of their setse. They are widest at 

 the center and taper somewhat toward either end. The basal third is 

 cylindrical in shape, while the terminal two-thirds is flattened or com- 

 pressed into a knife-blade form, the whole resembling in shape the 

 common form of paper cutter made from a cylinder. At the first moult 

 the skin over these anal appendages is shed exactly like that over the 

 others, but at the second moult the entire appendages disappear. 



After the first moult also the pigment extends in toward the center of 

 the bod}^, and by the second moult has become quite evenly distributed. 



Metanauplius. — Body elongated and narrowed, carapace covering 

 two-thirds the entire length (fig. 40 in text). Carapace ellipitical, 

 well rounded anteriorly, narrowed and emarginate posteriorly. Three 

 free thorax segments and a terminal segment representing the genital 

 segment and abdomen, as yet unseparated. The eyes are placed far 

 back, near the center of the carapace, and are fused on the mid line, as 

 in the adult. The rusty brown color covers a wider space along the 

 margin and is more uniformly disposed than in the nauplius. In place 

 of the three pairs of nauplius appendages there are five pairs of 

 thorax appendages. 



Anterior antenna? are two-jointed, bearing long seta? on the terminal 

 joint, irregularly disposed; basal joint closely approximated to the 

 anterior margin of the carapace. 



Second antenna? biramous; exopod short and rudimentary, ending 

 in a short spine; endopod longer and stouter, terminating in a curved 

 claw nearly as long as the endopod itself, and bent over ventrally until 

 its tip nearly touches the basipod (fig. 42 in text). 



First and second maxilla? very rudimentary, the former a mere pro- 

 tuberance near the margin of the carapace, the latter consisting of 

 a single conical spine at the side of the mouth (fig. 43). 



First maxillipeds shorter and stouter than in the adult, tipped with 

 three strong spines or claws, the two inner of which are pectinated. 

 Second maxillipeds longer and more slender than in the adult, pro- 

 jecting far beyond the edge of the carapace, the terminal claw with an 

 accessory spine on its inner margin. 



First two pairs only of the swimming legs present on the first two 

 free thorax segments; both pairs rudimentary, biramous, the terminal 

 joints fringed with plumose seta? (figs. 44, 45). Total length, 0.67 

 mm. Length of carapace, 0.42 mm.; width of same, 0.22 mm. 



This small species is very abundant upon the common bonito (Gyra- 

 nosarda pelamis Linna?us), but has not been found thus far upon any 

 Other fish. It frequents both the mouth and the gill cavity, more com- 



