336 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 21 



senting a plane surface, inner margins closely approximated ; merus trian- 

 gular, angles rounded, anterior margin broadly arcuate, no visible notch 

 for insertion of palpus. 



Chelipeds of male massive ; ischium with inner margin compressed ; 

 merus trigonal, inner margin compressed, outer margin tridentate; carpus 

 roughened, largest tubercle at inner angle; manus high, compressed, 

 margins subparallel, a double row of granules on inner surface ; dactylus 

 ridged, fingers denticulate throughout, gaping slightly at bases. Chelipeds 

 of female much smaller, proportionate to walking legs, which they re- 

 semble. 



Ambulatory legs strongly cristate ; merus with a superior crest culmi- 

 nating in a tooth ; carpus with a single triangular crest ; propodus with a 

 similar crest and a superior and inferior tubercle; dactylus as long as 

 propodus, curving, nail amber. 



Male abdomen set flush with concave surface of sternal plastron; 

 plastron outlined by a row of tubercles continuous with the two tubercles 

 of segment three; segment two with a low median tubercle, segments 

 three to five fused, segment six becoming broader distally, segment seven 

 longer than broad, tip narrowly rounded. 



Male first pleopod becoming increasingly curved and sclerotized 

 toward tip; tip appearing in terminal view as a triangle having the 

 opening of the sperm duct centered, protected by a shallow eave. (See 

 Plate T, fig. 8) 



A number of specimens in the present series, including the male de- 

 scribed, show a remarkable attenuation of the branchial ridges. This 

 character is associated with age and occurs in specimens as large as the 

 type (12.5 mm) or larger. Although first observed in Ecuadorean speci- 

 mens, it does not appear to be a geographical development, since speci- 

 mens taken in the Gulf of California in later years show this peculiarity 

 also. 



Material examined: 62 specimens from 23 stations. (See Table 69) 

 These range from Santa Maria Bay, Lower California, and Puerto 

 Refugio, Angel de la Guarda Island, Gulf of California, Mexico, to 

 Santa Elena Bay, Ecuador, and are distributed as follows: Mexico 9, 

 Costa Rica 4, Panama 6, Colombia 1, and Ecuador 3 stations. In addi- 

 tion to the above, 18 specimens from 12 Galapagos stations (Garth, 

 1946). 



Measurements: Male specimen: length 13.7 mm, width 17.3 mm, 

 rostrum. 3.7 mm, width 2.8 mm, cheliped 12.7 mm, chela 6.3 mm, dactyl 



