6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO3 



elongate but the dorsal and ventral extremities are irregular in out- 

 line; there are six to eight minute chitinous teeth along both the 

 anterior and posterior edges. The troughs of the postcephalosome 

 are irregular in shape but roughly cross-shaped with the vertical axis 

 longer than the horizontal axis ; there are four groups of one to four 

 teeth along the inner margin of these two troughs. The troughs of 

 the thorax and abdomen are situated in approximately the middle 

 of the segments. They are all similar, being long and narrow with 

 10 to 14 triangular interlocking teeth on each side. 



The location of the genital pore on the ventral side of the first 

 thoracic segment is indistinctly indicated by the presence of a broadly 

 obtuse chitinous ridge which projects anteriorly and ventrally near 

 the anterior margin of the segment. 



The first antennae are long and 8-segmented; the first three seg- 

 ments are short and broad, but the others are elongate, the terminal 

 segment being the longest. The first segment bears one seta; the 

 second has three, two of which are minute ; the third has seven, four 

 of which are minute ; the fourth through eighth segments bear 3, 4, 4, 5, 

 and 3 to 5 terminal setae, respectively. The first and second segments 

 each have a small dorsal hook, and the terminal segment bears a 

 single delicate aesthetask. 



The second antennae are biramous with the 5-segmented endopod 

 being about half again as long as the 9-segmented exopod. The basal 

 endopod segment bears two short median setae while the third seg- 

 ment has a single seta. The terminal endopod segment is long and 

 fingerlike and bears a fringe of fine hairs at its tip. The exopod 

 segments are short; segments one, four, five, and six have a single 

 short seta, while the seventh and eighth have a long plumose seta; 

 the terminal segment is tipped with three long plumose setae. There 

 are five aesthetasks, one oh the basipod, one on the first exopod 

 segment, one on the third, and two on the terminal segment. All 

 the aesthetasks project laterally. Because of their delicacy they are 

 often broken off in specimens which have been permanently mounted 

 on slides. 



The mandibles are of a generalized larval type. The 2-segmented 

 endopod is about two-thirds as long as the 7-segmented exopod. The 

 basal endopod segment bears a single median seta, while the other 

 has two median and three terminal setae. Exopod segments three, 

 four, five, and six bear a single terminal seta, the last three of which 

 are plumose. The last exopod segment has three terminal plumose 

 setae, two of which are short while the third is slightly more than 

 twice the length of the entire exopod. The basipod bears a single 



