PARASITIC C0PEP0D8—CAL1OTD.E— WILSON. 583 



wider than the neck of the median carapace lobe which joins it ante- 

 riorly, and passing- insensibly into the genital segment posteriorly. 

 Genital segment acorn-shaped, the anterior and posterior margins 

 straight and parallel, the former about half the latter, contracted 

 strongly where it joins the free segment. In the alcoholic specimen 

 the dorsal surface of this genital segment has a row of three pits or 

 depressions on either side of the midline, the two central ones being 

 connected across the midline by a groove which is convex anteriorly, 

 while the two anterior ones are joined similarly by a straight groove. 

 In the living specimens obtained by the author these pits and grooves 

 were almost invisible and would never have been noticed had not the 

 alcoholic specimen been studied first. 



Abdomen narrow and two-jointed, four times as long as wide, the 

 terminal joint two to two and a half times the length of the basal. 

 The latter is enlarged where it joins the genital segment and tapers 

 somewhat toward the distal joint which has parallel sides. The pos- 

 terior end of this distal joint is wedge-shaped and the anal lamina? are 

 attached to the sides of the wedge. They are long and narrow, cylin- 

 drical in form, and curved in toward each other at the tips, while the 

 plumose seta? which they carry are fully as long as the entire abdomen. 



The egg cases are the same width as the abdomen and about half the 

 length of the entire body. The eggs are quite thick and number 45 or 

 50 in each case. 



Of the ventral appendages the anterior antenna? are small, with the 

 t wo joints about the same length. The posterior antenna? are slender, 

 the terminal claw being but little longer than the basal joint. The 

 accessory spine behind the base of this antenna is long and sharp. 



The first maxillae are small, only slightly enlarged at the base and 

 with a blunt tip. The second maxilla? are simple, quite long and 

 nearly straight; each carries upon its base a raised papilla from whose 

 summit project two divergent seta* representing the exopod of the 

 appendage as in O. rapdx and several other species. First maxillipeds 

 of normal size and structure, bearing a small spine on the anterior 

 margin of the distal joint near the tip, and terminating in two curved 

 and winged claws of unequal length. The second maxillipeds are 

 peculiar. The basal joint is very large and as wide as it is long. It 

 sends out two protuberances on the inner margin, a large one at the 

 base which is hemispherical in form with a flattened tip, another still 

 larger at the distal end. This latter is broad and linger-like and extends 

 outward along the inner curve of the terminal claw, forming an inar- 

 ticulate half of a large chela, very similar to those borne by other 

 Crustacea. It is notched at the tip where it is also covered with short 

 and still' spines, making a rough surface admirable for retaining a firm 

 hold. The terminal claw is about two-thirds the length of the basal 



