NO. 1580. NEW SPECIES OF CALIGIN^— WILSON. 808 



well-developed cement glands were found which proved the sex 

 beyond a doubt. A second fact, therefore, would be that these glands 

 develop first in the growth of the sexual organs and furnish a sure 

 method of distinguishing the sexes. 



A third inference is in regard to the so-called fifth legs; if there is a 

 joint extending across the genital segment in front of them then they 

 must be the rudiments of the sixth rather than the fifth pair of legs. 

 When two pairs are visible upon the genital segment we call the 

 posterior pair the sixth and the anterior pair the fifth. But this 

 young female would seem to show that when only one pair are present 

 they are as likely to be the sixth as the fifth pair. A genital segment 

 which shows no signs of division in the adult may have been divided 

 in the young with sufficient clearness to indicate beyond a doubt 

 which pair of legs it is that are present. 



Total length, 3.3 mm.; length of carapace, 1.7 mm.; length of 

 free segment, 0.5 mm.; length of genital segment, 0.7 mm.; length 

 of abdomen, 0.7 nun.; width of carapace, 1.7 mm.; width of genital 

 segment, 0.4 mm. 



Nauplius. — Body ovate, evenly rounded anteriorly but quite 

 squarely truncated posteriorly between the balancers. Appendages 

 proportionally longer than usual, but otherwise of the ordinary 

 form. The entire center of the body filled with a mass of opaque 

 yellowish yolk granules, which extend forward in three lobes the 

 median of which is wider and blunter than the two lateral ones. 

 The balancers are long, cylindrical, and quite strongly curved; they 

 start out from the posterior corners at an angle of 45 degrees, but 

 curve forward so much that their terminal halves are in the same 

 straight line which is at right angles to the body axis. The pigment 

 is of a peculiar deep Prussian blue and is distributed in the form of 

 spots along either margin of the l)ody outside the yolk. There is a 

 large spot at the base of each balancer, and the two fuse across the 

 mid line. The eye spot is also large and covers the entire space 

 between the bases of the fh'st antennae. 



Total length, 0.22 mm.; width of body, 0.12 mm. 



This species was established by Heller in 1865 from specimens 

 found on the gills of " Pimelodus maculatus," a catfish common in 

 Brazil. The species has not been seen since, or at least has not 

 appeared in any published AVTitings. In the redescri])tion as here 

 given many interesting details have been added. 



The present specimens were obtained from two species of the same 

 family of catfish, namely Hexanematichthys felis Linnaeus and Felich- 

 thys marinus Mitchill. The former lot of specimens is Cat. No. 32804, 

 U. S. N. M., the latter Cat. No. 2800, U. S. N. M. On both fisli the 

 copepods were found in the gill cavity and on the inside of the 

 operculum, rarely more than three or four on the same fish. But 



