592 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvai. 



irreo-ular nuiroinal l>aii(l. And often tho pio-niont oxtend.s out into the 

 anttMHiulcs ahncst to their distal end and into the basipods of the other 

 two pairs of appendag^es. The balancers on either side of the anus 

 are long and stout (0. 12 by 0.01 nmi.), their length exceeding that of 

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

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

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

 pressed into a knife-blade form, the whole reseml)ling in shape the 

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

 the skin over these anal a[)pendages 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 body, and ))y the second moult has become quite evenly distributed. 



Jf<ft/?un/j}Iiiis. — Body elongated and narrowed, cara})ace covering 

 two-thirds the entire length (tig. 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 ]:)airs of nauplius a})pendages there are five pairs of 

 thorax appendages. 



Anterior antenme are two-jointed, bearing long set^e on the terminal 

 joint, irregularly disposed; ])asal joint closely api)roximated to the 

 anterior margin of the carapace. 



Second antennfx? 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 (tig. 42 in text). 



First and second maxilUe 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 (tig. 43). 



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

 three strong spines or claws, the two inner of which ai'c pectinated. 

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

 jecting far bevond the edge of the carapace, the terminal claw^ with an 

 accessory spine on its inner margin. 



First two pairs only of the sw^imming legs present on the first two 

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

 joints fringed with plumose setie (iigs. 44, 45). Total length', O.tlT 

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



This small species is very abundant upon the common 1)onito {(jyrn- 

 }i(/sarda pe/ffnu'.s Ijmui\}Uf>), but has not ])een found thus far upon an}^ 

 other lish. It frequents both the mouth and the gill cavity, more com- 



