14 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 121 



dently also overlooked the faint seta on the inner lamella in front of 

 the posterior process and the small bristle below the antennal sinus. 

 Shell dimensions (in mm) are as follows: 



specimen no. greatest length greatest height remarks 



1 0. 73 0. 46 whole specimen 



2 0. 64 0. 43 separated left valve 



3 0. 73 0. 48 separated right valve 



Miiller (1894, p. 212) gives a length of 0.93 mm for this species. 

 The smaller size of specimens available for the present study indicates 

 that they are instars. 



First antenna (figs. 7e,f): Second joint with 1 spinous dorsal bristle 

 and sparse clusters of spines on medial surface; 3rd and 4th joints 

 each with 1 ventral and 1 dorsal spinous terminal bristle; 5th joint 

 with 1 long ventral, terminal sensory bristle with forked tip; 6th joint 

 minute, welded to 5th joint, and with 1 short medial bristle; 7th joint 

 reduced, welded to 8th joint, and with 1 short spinous a-bristle, 

 1 short b-bristle with forked tip and 1 distal filament, and 1 long 

 c-bristle with forked tip; 8th joint reduced, with 2 long bare d- and 

 e-bristles, 1 long f-bristle and 1 long g-bristle, both with forked tips. 



The illustration of the 1st antenna illustrated by Miiller (1894, 

 pi. 3, fig. 48) bears 2 ventral bristles terminally on the 4th joint (con- 

 sidered 5th joint by Miiller). The presence of only 1 bristle in that 

 position on the specimen I examined may be due to its not being 

 adult. A few filaments were observed on long bristles of joints 5-8, 

 but it was not possible to determine the exact number and precisely 

 on which bristles they belonged. 



Second antenna (figs. 7g-i) : Endopodite (fig. 7h) single jointed, with 



1 long hirsute bristle and 1 short bare bristle. Exopodite with 9 

 joints: 1st joint slightly longer than total length of following joints; 

 2nd to 9th joints trapezoidal, each joint smaller than preceding joints, 

 all without basal spines; 2nd to 8th joints with long bristles with 

 stout spines along outer margin, becoming shorter, more slender, and 

 numerous at distal end; 9th joint with 1 short and 1 long spinous 

 bristle; all bristles without natatory hairs; distal margins of 2nd to 8th 

 joints with comb of slender spines; tip of bristle on 2nd joint not 

 reaching 9th joint. 



The 2nd antenna shown by Miiller (1894, pi. 3, fig. 35) is similar to 

 the specimen described in this paper. Miiller apparently over- 

 looked the row of short spines along the distal margin of joints 2-8 

 of the exopodite. 



Mandible (figs. 7j, k) : Coxale endite (fig. 7j) bifiu-cate with distal 

 spines. Basale with 7 bristles, 4 ventral, 3 dorsal. Exopodite with 



2 bristles, outer bristle shorter than inner bristle and with wreaths 

 of long hairs. Endopodite: 1st joint with 1 short and 2 long ventral 



