40 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 122 



Description of females in collection. — -Shell (figs. 17 a-g; pi. 4) : 

 Right valve ornamented, left relatively plain (pi. 4) ; caudal process 

 directed posteriorly (figs. 17a., b), with spines and bristles on lateral 

 surface (fig. 17(/); selvage narrow striated, (fig. 17^); lamellar pro- 

 longation of selvage with denticulate margin in some areas, becoming 

 wider around caudal process; adductor muscle scars obscure, con- 

 sisting of several ovoid scars anteriorly and ventrally to midvalve; 

 marginal flange narrow, becoming wider along ventral and posterior 

 margins, with numerous bristles and toothhke spines; false radial 

 pore canals numerous, normal pore canals sparse. 



Inner lamella with small bristle anteriorly (figs. 17a, b), 3 bristles on 

 caudal process (figs. 17c, e, f), 5 bristles near inner margin anterior 

 to caudal process, and, dorsally to caudal process, 6-7 bare bristles 

 followed by 2 hirsute bristles (figs. 17e,/). 



Dimensions of specimens in collection are as follows: 



First antenna (figs. \1h, i; 19k): 1st joint bare; 2nd joint with 1 

 dorsal bristle and 2 dorsal spines; 3rd joint with 1 dorsal bristle; no 

 suture between 3rd and 4th joints; 4th joint with 1 dorsal and 2 ventral 

 bristles distally; 5th joint with 1 long ventral bristle distally; 6th 

 joint with 1 short medial bristle distally; 7th-8th joints with 1 short 

 and 7 long bristles. 



Second antenna (figs, 17^*, 18a-c): exopodite with 9 joints; 1st joint 

 with short, curved terminal spine medially; 2nd-8th joints each with 1 

 bristle with natatory hairs; 9th joint with 1 long and 1 short bristle, 

 both, or only longer bristle, with natatory hairs; distal lateral margins 

 of 3rd-8th joints may have 2 or more small spines; endopodite 1- 

 jointed, with 2 proximal bristles and 1 short, unringed ventral bristle. 



The endopodite of the right 2nd antenna of USNM 113471 differs 

 from the left and also from USNM 113470 in having only 1 proximal 

 bristle. The 8th and 9th joints on the exopodite of the right 2nd 

 antenna on USNM 113470 are abnormal in being fused and in having 

 the long bristle on each joined together, forming a single forked 

 bristle (fig. 18c). The short bristle on the 9th joint of each exopodite 

 on USNM 113471 is shorter than the equivalent bristle on USNM 

 113470. 



Mandible (figs. 18d-4) : coxale with ventral fringe of short spines and 

 short ringed medial spine (spine not observed on right mandible of 

 specimen 113470); basale with 3 spinelike bristles dorsally and 1 

 lateral and 4-5 medial bristles ventrally; endopodite 3-jointed; 1st 



