THE CANCROID CRABS OF AMERICA 



461 



Diagnosis. — Orbital hiatus closed. Sides of carapace bidentate. 

 Fingers very long. 



Description. — Carapace slightly convex in both directions, about 

 three-fourths as long as wide, antero-lateral margins arcuate, postero- 

 lateral sinuous, rapidly converging. Surface smooth, microscopic 

 granulation near front and lateral teeth. Front nearly half width of 

 carapace, slightly arcuate, almost imperceptibly bilobed, edge thin, 

 retreating at outer angles; just behind and parallel to the margin is 

 a sharp ridge slightly interrupted at middle. Orbit less than half as 

 wide as front; upper margin oblique, outer angle not advanced. 

 Margin between orbit and first lateral tooth crenulate. Tooth at 

 lateral angle subacute, a little in front of middle of carapace ; anterior 

 tooth obtuse, about one- 

 third distance from or- 

 bital angle to lateral tooth. 

 Abdomen of mature 

 female narrow; third, 

 fourth, and fifth segments 

 subequal in length as well 

 as in width; sixth of same 

 width but longer; seventh 

 narrower, length and 

 breadth subequal, ex- 

 tremity rounded. 



Arm extending but little 

 outside carapace, trigonal, 

 widest near middle; car- 

 pal tooth large, spiniform. 

 Hand with inner surface 

 swollen toward proximal end; margins smooth, rounded; superior 

 margin slightly convex, inferior sinuous, that of fixed finger con- 

 cave. Dactylus longer than superior margin of palm. Fingers not 

 gaping, a few lines of punctae; dactylus without teeth; larger fixed 

 finger with one low tooth on basal half and two teeth and a few 

 denticles on terminal half; in smaller chela, the teeth are all on 

 terminal half. Legs as in Trapezia; dactyli nearly as long as propodi. 



Measurements. — Ovigerous female, length of carapace 7, width of 

 same 9.7, fronto-orbital width 7.2, width of front 4.4 mm. 



Range. — Off Chatham Island, Galapagos Islands; lat. 0° 50' 00" 

 S., long. 89° 36' 00" W.; 45 fathoms; gy. S.; temperature 74.1° F.; 

 April 4, 1888; station 2809, Albatross; 1 ovigerous female, holotype 

 (21586). 



Figure 76.— Ectaesthesius bifeons, female, holotype, 

 carapace 9.7 mm. wide. a. outer maxilliped. 6. front 

 VIEW. c. Dorsal view 



