78 U.S. NATIONAL MUSEUM BULLETEN 292 



narrow posterior rectangular bands; remaining terga with single 

 rectangular band; upper margins of bands, except those in first 

 abdominal somite partially edged in dark blue. Translucent longi- 

 tudinal band on tergopleural junction encompassing dark blue longitu- 

 dinal stripe extending from articular knob between first and second 

 abdominal segments to that between fifth and sixth, band darkest 

 and broadest at knobs, becoming more diffuse posteriorly from each 

 knob and progressively narrower and less distinct posteriorly. Dorsal 

 portions of pleura crossed by longitudinal hght stripe, flanked ventrally 

 by bluish green band, and latter flanked ventrally by another pale 

 band. Ventral half to three-fifths of pleura pale bluish green and 

 translucent, with longitudinal row of five prominent dark blue spots 

 on level with posteroventral spot on carapace; anterior three spots 

 spanning second pleuron, fourth on fourth pleuron and last on fifth. 

 Sixth abdominal somite with similarly colored spot on posterolateral 

 margin contiguous with spot on anteromedian margin of telson. 



Eyestalks, antennular and antennal peduncles, and anterolateral 

 surfaces of coxae of pereiopods with dark blue spots; appendages 

 otherwise translucent bluish green except for scarlet tips of chelae 

 of first and second pereiopods bearing grayish-tan setal tufts. 



Material examined. — The Dominican collections contain 7 males 

 (carapace lengths 3.7-4.2 mm), 17 females (cl 2.2-6.9 mm), 1 of 

 which is ovigerous (cl 6.2 mm), and 3 juveniles (cl 1.3-1.8 mm). 

 All of the males have the appendix mascuhna on the second pleopod 

 fully formed. 



Ecological notes. — A rubble bottom and moderately swift to 

 swift current typify all of the localities in which P. glabra was found. 

 Only at station 105 was the collector aware that he was collecting 

 specimens of this species at the time that he took them. Here, just 

 below a small waterfall is a pool of clear water, some 15 to 20 feet in 

 diameter, from which the water flows in several narrow channels over 

 moss-covered stones and rubble. The 10 specimens taken in this locality 

 were obtained by placing a net downstream from the beds of rubble 

 and scouring the accumulation of small stones and sand and by 

 thrusting a small net into the mats of submerged moss. Along with 

 the 10 specimens of Potiminm, 70 specimens of Atya innocuous were 

 secured, most of which were approximately the size of the Potimirim. 

 This locality (see Mitchell, 1966, pp. 90-91) is on the northeastern 

 slope of Morne Trois Pitons on a tributary to the Fond Figues Kiver 

 at an elevation of slightly less than 1,400 feet. 



Distribution. — Dominica, republics of El Salvador, Nicaragua, 

 and Costa Rica, and Rio de Janeiro and Sao Paulo states, Brazil. 



Dominica Stations: 26, 32, 39, 55, 63, 75, 76, 81, 105 (25-1,350 ft.). 



