238 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 24 



just behind them, and one on middle or proximal third of posterior 

 margin; that of leg 3 over twice as long as wide. Dactylus with four 

 fixed spines, distal three large, curving inward, proximal one small, 

 curving outward. 



Telson of abdomen composed of seven plates. 



Material exa?nmed: See Table 70. 



Measurements: Males, 3.4 to 8.4 mm; non-ovigerous female, 9.3 

 mm; ovigerous females, 7.0 to 10.4 mm. The ovigerous female holotype 

 is 9.1 mm in length, 13.5 mm in breadth. Glassell recorded a measure- 

 ment of 10.2 by 15.5 mm for a female specimen. 



Color: In life, ground color of carapace and chelipeds dark brown, 

 mottled with green and red ; legs lighter and banded ; abdomen mottled 

 and opalescent. (Glassell) 



Ecology: "This species is found commensal with the chaetopodous 

 annelid, Chetopterus variopedatus (Renier), which was found in a 

 leathery double-ended tube, located at mean low water level, on an eel 

 grass mud flat. Only the larger tubes were found to have crabs in 

 them. These tubes are about a yard long by an inch in diameter." 

 (Glassell) The Velero III and Velero IV have dredged it in 2-25 fath- 

 oms, on bottoms of mud and sand and of coralline and rock; it was 

 taken once from kelp holdfasts in 12-15 fathoms and twice from worm 

 tubes in 8 and 18 fathoms, the worm being specified as Chaetopterus 

 in the former case. The U. S. National Museum specimens collected by 

 the Orca in 11 fathoms were from Chaetopterus tubes. 



Ovigerous females have been collected in January, June, and Sep- 

 tember. 



Relationships : In a recent review of Indo-Pacific Poly onyx, John- 

 son (1958) noted that the species fall into three natural groups. All 

 the known American species {P. gibbesi Haig^ and the three treated 

 in this report) clearly belong to Johnson's "P. sinensis group," char- 

 acterized by him as follows: "Lateral margins of the carapace without 

 spines. Carapace broader than long, transversely ovate, or rectangular 

 with rounded corners. Front rather narrow, trilobate with the median 

 lobe broad and rounded and projecting little beyond the lateral lobes, 

 which are often scarcely developed so that the front is almost straight. 

 Chelipeds with the anterior margins of the carpus and merus unarmed ; 

 a more or less marked development of hairs on their outer, and often 



1 Substitute name for P. macrocheles (Gibbes) ; see Haig, 19S6a, p. 29. 



