Figure 188. — Pinnotheres ostreum Say. A, stage I female 

 in dorsal view ; B, stage I female in ventral view ; ap- 

 proximately X 9 (after Stauber, 1945). 



Figure 189. — Pinnotheres ostreum Say. Male in dorsal 

 view, walking legs of left side not shown, 1 mm. indi- 

 cated. 



orly. Outer niiixilliped with ischium and merus 

 fused: carpus, or first article, of palp short, ob- 

 long; propodus elongate, end rounded; dactyl 

 inserted behind middle of propodus, minute, 

 si i> n dei-. 



Chelipeds small ; merus and carpus rather slen- 

 der. Palm somewhat flattened inside, swollen 

 outside, strongly widened from proximal toward 

 distal end, then narrowed; width across base of 

 Angers less than greatest width of palm; fingers, 

 especially immovable one, stout, not gaping, tips 

 hooked past each other, minute teeth on opposed 

 edges, a larger tooth near base of each, immovable 

 finger horizontal. Walking legs slender, subcylin- 

 drical; last two articles with thin fringe of hair; 

 second and third legs about equal in length, first 

 legs slightly stouter, last pair turned backward 

 and upward. 



Abdomen large, extending beyond carapace in 

 all directions. 



Measurements. — Carapace : width, ranging from 

 4 to 15 mm. (Christensen and McDermott, 1958). 



Color. — Whitish or salmon pink. 



Recognition characters. — Mature male and 

 hard-stage female : Carapace well calcified, flat 

 dorsally, subcircular in outline, with truncate 

 front more advanced than in mature female. 

 Posterior margin straight ; lateral margin thin, 

 rather sharply bent from dorsal side, margin 

 marked by a raised band of short dense hair. Eyes 

 well developed. Buccal mass crescentic, arched, 

 broad from side to side but short anteroposteri- 

 orly; cavity completely closed by external maxih 

 lipeds formed as in mature female. 



Chelipeds stout; merus and carpus not slender 

 as in mature female. Palm slightly flattened in- 

 side, swollen outside, and shaped as in mature 

 female, both margins convex. Hand with bands 

 of pubescence on upper and outer surface of palm, 

 and outer surface of immovable finger. Fingers 

 stout, especially immovable finger, with tips 

 hooked past each other when closed; dactyl with 

 small tooth proximally, tooth fitting between two 

 protuberances on immovable finger when closed; 

 both fingers with stiff hairs on gripping edges. 

 Walking legs flattened, with posterior margins 

 thickened, and with plumose swimming hairs on 

 second and third pairs. 



Abdomen narrow, confined to sternal depres- 

 sion; copulatory stylets of male well developed, 

 first pair bladelike and hairy, second pair rodlike 

 and almost hairless (Stauber, 11)45). 



204 



FISH AND WILDLIFE SERVICK 



