North American Centropagidce. 261 



(furca included) ; produced on the right side into a slight 

 semicircular process. Third segment and furcal rami sub- 

 equal, each slightly longer than the fourth segment. Furcal 

 rami very broad and delicately hairy within ; armed at the 

 outer apical angle with a short, sharp broad spine (the one 

 on the right ramus the larger), and within this with three 

 delicately plumose apical setpe, the outer of which, at the base 

 and for a considerable part of its length, is even broader than 

 the spine but gradually tapers and ends in a delicate flagellum, 

 while the other two sets are much narrower than the outer 

 seta but about as long. At the inner apical angle is a much 

 smaller delicate smooth seta. Abdomen of male much 

 more strongly flexed to the right than that of female, com- 

 posed of six segments (furca included), the second, third, 

 and fifth produced on the right side. First segment short, 

 about twice as broad as long. Second segment somewhat 

 longer than the first, the process about as long as the segment 

 is wide, with a smooth anterior margin and an irregularly 

 serrate inner margin with a hooked tip. Third segment about 

 as long as the first ; process about as long as the segment, 

 ..of nearly the same width throughout, the tip bluntly rounded 

 and armed anteriorly with a hemispherical tuberculate 

 cushion or pad, and on the posterior margin, almost opposite, 

 with another similar process. Fourth segment slightly longer 

 than the third, and unarmed. Fifth segment slightly shorter 

 than the fourth and armed with two processes, the anterior 

 of which is perfectly smooth, pointing forward and to the 

 right, the posterior one pointing almost straight to the right,, 

 armed on the anterior margin with a number of large teeth 

 (8 — 10), its posterior margin smooth at the tip but minutely 

 denticulate for the basal three fourths. Furcal rami armed 

 about as in the female but with no such difference in the width 

 of the apical setae and with narrower spines. 



Antennas 2 5 -segmented, extending to the posterior margin 

 of the fourth abdominal segment. Right male antenna slen- 

 der, geniculate between the 18th and 19th segments; seg- 

 ments 19 — 21, and 22 and 23 ankylosed ; antepenultimate 

 segment without special armature. 



