no. 2354. NEW SPECIES OF PARASITIC COPEPODS— WILSON. 9 



TREBIUS LATIFURCATUS, new species. 



Plate 4, figs. 28-3-1. 



Host and record of specimens. — About 25 females were taken by 

 Dr. A. B. Ulrey from the outside surface of four different kinds of 

 fish in the aquarium of the marine station of the University of South- 

 ern California at Venice, California, August 4, 1919. The fish which 

 served as hosts were the small sting ray, Urolophus halleri, the Cali- 

 fornia sting ray, Myliobatis calif ornicus, the marbled ray, Pteroplatea 

 marmorata, and the bastard halibut, Paralichthys californicus. 



One of the females with fully developed egg strings has been 

 selected as the type of the species and has been given Cat. No. 53551, 

 U.S.N.M. ( 



The remaining specimens become paratvpes, with Cat. No. 53552, 

 U.S.N.M. 



Specific characters of female. — Carapace suborbicular, wider than 

 long, evenly rounded anteriorly, but quite squarely truncated pos- 

 teriorly. Frontal plates broad and well rounded, their combined 

 length about three-sevenths of the width of the carapace. Trans- 

 verse grooves dividing the lateral areas placed farther back than 

 in any other species. Eyes fused on the midline and very distinct. 

 Third thorax segment nearly one-half wider than the fourth, but 

 not as long. Fourth segment barrel-shaped, wider than long. Genital 

 segment half the width and two-thirds the length of the carapace, 

 flask-shaped, narrowed into a short neck anteriorly as it joins the 

 fourth segment and posteriorly as it joins the abdomen. 



The posterior corners are rounded and armed with spines. The 

 egg strings are about the same width as the abdomen and do not 

 quite reach the tip of the latter ; eggs small, 25 to 30 in each string. 



Abdomen one-half longer than the genital segment and less than 

 one-third as wide, three- jointed, the terminal joint indistinctly sepa- 

 rated from the subterminal. The entire surface of all three joints 

 is sparsely covered with tiny spines. Anal laminae long and nar- 

 row, armed with short spines on the outer margin and at the end, 

 but with long capillary setae on the inner margin. 



First antennae long and narrow and projecting prominently. Ter- 

 minal claw of the second antennae as thick as the basal joint and 

 abruptly curved near the tip. Maxillary palp S shaped, with the 

 basal portion slightly enlarged and the tip bluntly rounded. Basal 

 joint of the first maxillae fused with the ventral surface of the head 

 and furnished with a rudimentary exopod in the form of two long 

 spines ; endopod broad at the base and then abruptly narrowed to a 

 bifurcate tip, the branches of which are slender and of the same 

 length. Furca small, the rami longer than the basal portion, flat- 

 tened and considerably enlarged at the tip. All the swimming legs 



