110 UNITED STATES NATIONAL MUSEUM BULLETIN 29 6 



mouthparts. The mandibles are extremely light and delicate. They 

 cannot be studied adequately by removing the mouthparts because of 

 their delicacy and their position. Thus, they can best be seen in the 

 KOH-corroded whole animal (fig. 28j). The anterior cutting edge is 

 serrated with numerous (about twelve) extremely fine teeth, three of 

 which are slightly more prominent. These teeth form a reasonably 

 straight line. Many light hairs are distributed along the ventral margin. 



The first maxilla is typical of the genus: a long, relatively straight 

 appendage with a tuft of long, heavy hairs at the e d (fig. 28k) . There 

 does not appear to be the pair of spines constituting the teeth of this 

 maxilla, as is found in most other genera. The apodeme of the first 

 maxilla is the typical long chitinous muscle-supporting rod bent at the 

 end into what resembles a hockey stick. 



The second maxilla is typical of the order: a pair of flat, hairy plates 

 closing the posterior mouth field, with a hairy process extending 

 anteriorly from the medial edge between the other mouthparts. 



Extending dorsally and then posteriorly from the mouth is the 

 esophagus, which leads into the gizzard, typical of the family. The 

 gizzard is an apparatus equipped with muscles and a set of central 

 teeth, followed by what appears to be a straining device. It is un- 

 doubtedly used to triturate the food. Its use notwithstanding, there 

 often appears heavy particulate food material in the gut following 

 the gizzard. The anus opens dorsally between the pairs of cirri. 



On the dorsal surface of the thorax are two unpaired filamentary 

 processes, similar to those of other members of the genus, and similar 

 to structures found in the order Thoracica. They are long, tapered, 

 annulated, flexible appendages set with a multitude of extremely short 

 hairs. Inasmuch as one or both can be turned back along the thorax, 

 they are sometimes difficult to observe clearly and hence can be missed. 



The posterior portion of the thorax tapers to the point of attachment 

 of the cirri. The dorsal surface is equipped with one prominent and 

 one lesser V-shaped chitinous thickening which apparently reinforces 

 the thorax. These areas bear especially prominent fine striations, which 

 may extend across the entire thorax. These fine striations are typical 

 of the order. 



The mouth cirrus is missing completely. In the entire genus the 

 mouth cirrus is reduced, with the greatest development exhibiting 

 only small, unsegmented appendages bearing a few bristles. No such 

 appendages can be seen in this species. 



The cirri are restricted to the posterior end of the thorax, and consist 

 of three pairs without a caudal appendage. The cirri are multiseg- 

 mented and biramous, on a two-segmented protopod. The protopod 

 bears a slanting articulation, with the distal segment much shorter 



