NO. 9 A NEW ORDER OF CRUSTACEA — PENNAK AND ZINN 7 



distal median seta and a prominent, curved, stout, spinelike gnathobase 

 which has several small median spinules. All the segments of the 

 mandibles are beset with small rows of fine hairs. 



The seven segments of the uniramous first maxillae are somewhat 

 broad and flat, the third segment being the largest. The basal segment 

 is narrowed at its base where it is attached to the trunk ; the second 

 segment is short and is set off from the first and third segments by 

 poorly defined articulations. Except for one small lateral seta on the 

 sixth segment, all of the setae are stout and are arranged along the 

 median margins of the segments (median and terminal margins in 

 the case of the last segment). Beginning with the basal segment the 

 setation of the first maxillae is 3-1-4-2-2-2-8. All of the setae except 

 those of the terminal segment are borne on small projections. 



The uniramous 6-segmented second maxillae are narrower and 

 slightly longer than the first maxillae. The first and second segments 

 are considerably larger than the other four. Like the first maxillae, 

 these appendages are densely setose along the median margins; 

 typically, the setation is 8-8-2-2-2-5. Three of the setae of the basal 

 segment are borne on a prominent process ; two setae of the terminal 

 segment and one on the fifth segment are geniculate. 



The structure of the postcephalosome appendages (maxillipeds) 

 is unique. They are small, irregular, but somewhat elongate, and 

 usually lie appressed to the trunk. It is likely that several exopod 

 and endopod segments have become fused with the basipod to form 

 the main body of the maxilliped. The remnant of the exopod con- 

 sists of three small segments, the second and third of which bear two 

 setae. The remaining endopod segments comprise a small bilobed 

 outgrowth which bears five setae. The large basal portion of this ap- 

 pendage has three small lateral and two small median processes all 

 of which bear one or two broad setae. 



In studying the first antennae, first maxillae, second maxillae, and 

 maxillipeds of about 20 specimens, it was found that there are occa- 

 sional variations in the number and precise positions of the setae. 



The four pairs of thoracic appendages are small, simple, unseg- 

 mented lamellae which lie rather closely appressed to the trunk. They 

 are all about the same size and differ only slightly in shape. The first, 

 second, and fourth appendages are roughly oblong, while the third 

 is tapered slightly, is more ovate, and has a small median notch at 

 about half length. The first abdominal appendages have two terminal 

 setae, while the others have three terminal setae. 



From the tip of the rostrum to the posterior end of the caudal 

 rami the length of the adult ranged from 409 to 491 microns; the 

 average length was 458 microns. 



