NO. 2117. DIAPT0MU8 VIROINIENSIS AND D. TYRELLI— MARSH. 459 



length. The tenninal hook is much shorter than the second seg- 

 ment of the exopodite, is stout, and symmetrically sickle shaped. It 

 is denticulate on its inner margin. The right endopodite is 1-seg- 

 mented, triangular in shape, and about equal in length to the first 

 segment of the exopodite. The left foot, in length, nearly reaches 

 the end of the first segment of the exopodite of the right foot. The 

 second basal segment is about as broad as long, the inner margin 

 being somewhat longer than the outer. The lateral hair is near the 

 distal angle. The fii-st segment of the exopodite is longer than wide, 

 the distal end being about half as wide as the proximal. The second 

 segment of the exopodite is slender and bears on about half its inner 

 margin a setose pad. It is terminated by a digitiform process, on the 

 inner margin of which is a falciform, clawlike spine. 



Length of female exclusive of f ureal setae, 1.366 mm. 



Length of male exclusive of f ureal setae, 1.24 mm. 



This species was found in material collected by Mr. H. K. Harring 

 in Black Pond, Virginia. 



It seems to be most nearly related to D. hirgei. 



Type-specimen. — Male Cat. No. 47892, U.S.N.M. 



Paratypes, one female Cat. No. 47897, U.S.N.M., and one slide males 

 and females, 9 specimens. Cat. No. 47893, U.S.N.M. 



DIAPTOMUS TYRELLI Poppe. 



1888. Diaptomus tyrelli Poppe, p. 150. 



1889. Diaptomus tyrelli De Guerne and Richard, p. 39, pi. 1, figs. 17-18; pi 



4, fig. 26. 

 1895. Diaptomus tyrelli Herrick and Turner, p. 76, pi. 10, fig. 19. 

 1897. Diaptomus tyrelli Schacht, p. 176. 



1907. Diaptomus tyrelli Marsh, p. 441, pi. 19, figs. 2, 3, and 8. 

 1915. Diaptomus pribilofensis, Juday and Muttkowski, p. 25, fig. 2 a, b, and 



c; fig. 3 a and b. 



Of medium size. The suture of the first cephalothoracic segment is 

 rather distinct. The first segment is considerably less in length than 

 the three following. The last cephalothoracic segment is expanded 

 into large lateral processes, each process armed with two spines. 



The first segment of the female abdomen equals in length the rest of 

 the abdomen. It is broad, dilated in front, and moderately dilated 

 laterally. It bears prominent lateral processes which are tipped with 

 acute spines directed backward. The second segment is shorter than 

 the third, and the two together are somewhat longer than the furca. 

 The furcal rami are stout and ciHate on both the inner and outer 

 margins. 



The antennae are 25-segmented and reach to the furca or to the 

 end of the furca. The antepenultimate segment of the right antenna 

 of the male is unarmed or has a small hyaline lamella, which may be 

 just visible at the distal end of the segment or may extend over the 

 distal third of the segment. 



The fifth feet of the female are slender. The spines of the first 

 basal segments are small and acute. The lateral hair of the second 



