PARASITIC COPEPODS — WILSON 555 



abdomen length. The caudal rami are lateral upon shoulders of 

 the sides of the sinus as in the female. Here that portion of the 

 sinus anterior to the caudal rami is closed so that the rami appear 

 to be basal, but even the pressure of a cover glass is sufficient to open 

 the sinus and show that the rami are really lateral. 



The antennae and maxillipeds are like those of the female except 

 that the spines on the basal plate of the latter are short and stout 

 and not very pointed. The swimming legs are simple and without 

 accessory sex characters ; the boot on the fourth basipod has no heel 

 but the toe is longer and more pointed than in the female and nearly 

 the whole boot is visible in dorsal view. Total length, 2.6 to 2.8 mm. 



Remurks. — This is the next to smallest species thus far described 

 and its diminutive size, together with the relative shortness of the 

 carapace, the shoulders on the sides of the posterior sinus of the 

 abdomen, and the peculiar shape of the respiratory areas are its 

 distinguishing characters. 



ARGULUS LONGICAUDATUS, new species 

 Plate 23, Figuees 49-56 



One female and one of two males taken from the outside surface 

 of a crappie {Pomoxis amndaris) caught in Lake Dallas, Tex., have 

 been designated holotype and allotype of the new species, U.S.N.M. 

 No. 78892. 



Female. — Carapace elliptical, one-fourth longer than wide, narrowed 

 a little anteriorly but still broadly and evenly rounded, with the pos- 

 terior lobes just reaching the anterior third of the third thoracic seg- 

 ment. The compound eyes are small, far forward, and vrell separated ; 

 the cephalic area is a little more than half the carapace length. The 

 respiratory areas are very indistinct; they consist of a large posterior 

 curved area and a minute, circular anterior area, the two areas well 

 separated. The second, third, and fourth thoracic segments diminish 

 in width and length backward. The abdomen is obovate, nearly as 

 long as the four thoracic segments combined and a little less than 

 twice as long as wide. The posterior sinus is three-quarters of the 

 entire length and the lobes taper rapidly distally and end in sharp 

 tips. The seminal receptacles are small, circular, and close to the 

 anterior margin ; tl^e caudal rami are basal. Through its basal por- 

 tion in front of the posterior sinus the abdomen is one-third wider 

 than the thorax and its anterior corners are broadly rounded. 



The first and second antennae are slender and of about equal length ; 

 in the first pair the basal segment has a blunt spine at its inner 

 corner, the second segment has a small straight spine on its anterior 

 margin, and the curve of the lateral claw reaches the center of the 



