42 UNITED STATES NATIONAL MUSEUM BULLETIN 296 



The mouthparts are quite typical. An unpaired rounded labium is 

 situated anteriorly to paired mandibles with palps, and two pairs of 

 maxillae. The mandibles bear three heavy teeth and a cluster of three 

 or four small teeth along the cutting edge from anterolateral to postero- 

 medial. The lateral flat surfaces are equipped with bristles, as is the 

 medial edge posterior to the cutting edge (fig. 3e) . 



The first maxilla bears two strong curved teeth and a few fine bristles 

 anteriorly, a clean notch, and a broad edge bearing numerous bristles 

 in two sets (fig. 3f). The usual long, curved apodeme extends from the 

 base of the first maxilla (fig. 3a) . 



The second maxilla is broad, heavily bristled, and closes the posterior 

 of the mouth field. 



The first pair of cirri, located close to the mouthparts and hence 

 called the mouth cirri, are biramous and appear to possess four and 

 three segments in the anterior and posterior rami, respectively. These 

 segments are diflBcult to count because of the numerous heavy bristles, 

 and the questionable presence of a tiny segment at the extreme tip 

 of each ramus. The rami are set on a two-segmented protopod. The 

 larger proximal segment is ornamented posteroventrally with a row of 

 fine nodules which appear to be invaginations of the chitinous integu- 

 ment. The bristles on the rami are in distinct tracts, primarily on the 

 margins and along the inner surface of the larger anterior ramus, the 

 latter bristles being somewhat plumose. The smaller posterior ramus 

 overlaps on the outside of the larger anterior ramus near the base. 



The other five pairs of cirri are crowded together at the tip of the 

 thorax, hence the name "acrothoracica." These are designated the 

 terminal cirri, and are numbered cirrus two to six, or terminal cirrus 

 one to five. The first terminal cirrus (cirrus 2) is shorter and weaker 

 than the others, which are quite similar to each other in size and shape. 

 All are biramous on two-segmented protopods, with all segments 

 bearing multiple sets of bristles. The last cirrus (6) bears extremely 

 fine bristles anteroventraUy. The bristles are primarily on the medial 

 surfaces of the protopod. The basal segment of the protopod is about 

 three times as long as the distal segment. 



A detail of the setation of a midportion of the last (6th) cirrus can 

 be seen in figure 3i. The alternation of a pair of long distal setae and 

 a pair of short central setae along the inner curvature of the cirrus 

 is typical, as is the unpaired seta on every second to fifth segment 

 along the greater curvature. There is no small unpaired seta between 

 the longer pairs on the inner curvature, as is found in some species, 

 but there is a small bristle in front of the unpaired seta on the outer 

 curvature. 



