A NEW SPECIES OF CORYCAEUS — WILSON 325 



spinous process. Setae short, not reaching to the distal end of the 

 terminal inside spine. 



Leg 4 like that of the female, except that the inside protuberance 

 of the second basal segment is not quite so large, the outer margin 

 lacks the setose hump, and the first exopod segment is wider, with its 

 spine reaching a little beyond the distal end of the second segment. 



Remarks. — This species occurred in the Beaufort and Gulf of 

 Mexico collections with Gorycaeus amazonicus F. Dahl. The two are 

 apparently the chief representatives of the subgenus Ditrichocory- 

 caeus on the American Atlantic coast. C. amazonicus was originally 

 described from near the mouth of the Amazon River, and M. Dahl 

 (1912) has reported it farther south along the Brazilian coast and 

 from the coastal waters of the Tortugas and Bermuda Islands. 

 Gorycaeus lubbockii Giesbrecht, with which C. B. Wilson confused 

 G. americanus, has been shown by M. Dahl (1912) and Gumey (1927) 

 to be an Indo-Pacific form of the subgenus. 



G. amoBonicus and G. ainericajius are similar in size and in certain 

 distinguishing characters of the appendages. They are the only 

 species of the subgenus having the terminal portion of the exopod of 

 the male first leg incised, and the inside spine thus set somewhat at an 

 angle; this is most pronounced in amazonicus. Likewise, they alone 

 have the spines of the first and third segments of the exopod of the 

 fourth leg so elongate. In the male of G. amazonicus, this condition 

 is apparently somewhat variable, some specimens examined having 

 the spine of the first segment reaching well beyond the middle of the 

 third segment. The arrangement of the setae of the third segment of 

 the fourth leg is also similar in the two species, but they differ in 

 having the protuberance of the second basal segment scarcely developed 

 in G. amazonicus, and in the relative proportions of the segments of 

 the exopod — in G. amazonicus the second and third segments are 

 subequal. 



Both females of the two species have the genital segment inflated 

 dorsally but are easily distinguished from one another by the relative 

 proportions of the abdominal segments and caudal rami. The genital 

 and anal segments of G. amazonicus are approximately equal (the anal 

 only a little longer in lateral view), and the caudal rami are only 

 slightly longer than the anal segment. In addition, the wings of the 

 third thoracic segment are exceptionally long, reaching to the distal 

 end of the genital segment. In the male of G. amazonicus, the anal 

 segment is about two-thirds the length of the genital, and the caudal 

 rami are slightly longer than the anal segment. 



The proportions of the two segments of the abdomen of Gorycaeus 

 americanus approach most closely those of the females of G. africanus 

 F. Dahl and G. farrani Fruchtl. Both of these species are also dis- 



