4 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 64. 



The two outer teeth of this plate are so close together and so far 

 removed from the inner one that it seems as if there must have been 

 originally a single tooth at each corner of the plate, and that the 

 outer one subsequently divided. 



The second feature is easily overlooked in the adult and has not 

 been noted hitherto. On the endopods of the third and fourth legs 

 in both sexes, at the distal end of the basal joint and on the anterior 

 margin is a finger process extending obliquely outwards. These 

 processes in the male are larger than in the female, and in both sexes 

 those on the fourth legs are longer than those on the third legs. 



A third feature is the boot-shaped lamella at the base of the fourth 

 legs in the female. These are larger than those of the male and have 

 a pronounced heel (fig. 9). 



Remarks. — It is well that these two verj^ large argulids should 

 be thus identified, but the very fact that an exceptional abundance 

 of material has led to this result suggests that other closely related 

 species might share the same fate if they could be bred in sufficient 

 numbers. The larger the species the better it seems to thrive when 

 breeding upon fish in captivity. Argulus mississippiensis and A. 

 lepidostei breed in large numbers upon the gars used in experiment 

 work at Fairport, Iowa. The present author, assisted by Mr. H. W. 

 Clark, picked over 1,200 specimens of these two species of parasites 

 from three rather small gars at Fairport, September 3, 1920. 



ARGULUS PAULENSIS, new species. 



Plate 1, figs. 1-5. 



Host and record of specimens. — Two females and a male of this 

 new species were taken from the outside surface of a fresh-water 

 fish called by the natives " Talrirana " at Itatiba, Sao Paulo, Brazil. 

 Both females contained eggs nearly ready for laying, and the larger 

 one w^as evidently fully matured. The three have been given Cat. 

 No. 54111, U.S.N.M., and the larger female is made the type of the 

 new species. 



Specific characters of the female. — Carapace orbicular, a little wider 

 than long and three-fourths of the entire length, but not covering 

 the bases of the third and fourth legs. Posterior sinus wide and 

 shallow, one-fifth the length of the carapace, its lateral margins 

 widely divergent; posterior lobes broadly rounded. Free thorax 

 narrowing rapidly posteriorly; abdomen elliptical, one-fourth longer 

 than wide; anal sinus wide and about one-quarter the length of the 

 abdomen (28 per cent) ; anal laminae subbasal, long and narrow. 



First antennae long and moderately stout, no hook or spine on 

 the anterior margin ; lateral hook as long as the terminal portion and 

 strongly curved. Second antennae short and rather stout. Eyes 



