PART 1 GARTH : PACIFIC OXYRHYNCHA 333 



Description: Surface covered with a dense, short, vascular pubescence. 

 Carapace with two median tuberculated prominences, gastric higher than 

 cardiac, continued along median line to posterior margin. Ridge running 

 obliquely backward from gastric prominence almost entirely occupied by 

 two protuberances, one at its middle and one at posterolateral angle of 

 carapace; carapace presenting a rounded or obliquely truncate outline. 

 Sinus of posterolateral margin more shallow than in Lissa bicarinata. 

 Margin of hepatic region with a tubercle ; of branchial region with sev- 

 eral tubercles and a blunt tooth at middle. Hepatic region nearly vertical. 

 Front with a shallow median emargination, from this the margin sloping 

 obliquely backward or almost transverse; outer corners with a slight 

 tooth, most produced in the young. Preorbital tooth subacute or obtuse. 



Chelipeds heavy in male ; ischium with tooth on inner margin ; merus 

 with tridentate crest on superior margin; carpus with surface uneven, 

 tubercle at inner angle. Hands broad, compressed, widening distally, 

 inner surface tuberculate ; lower margin of propodus with a sinus near 

 its middle ; dactylus with acute upper margin ; fingers gaping for basal 

 half. Chelipeds of female much smaller. Legs cristate; crest of merus 

 with a thin triangular tooth at distal end; carpus with two triangular 

 crests side by side, divergent, forming a cup ; propodus with a triangular 

 superior crest, a tubercle on anterior and posterior surfaces, and with 

 swellings at articulation with dactylus. (Rathbun, 1925, modified) 



Male abdomen with segments 3-5 fused ; segments two and three 

 strongly tuberculate; greatest width opposite segment three, least width 

 at base of segment six; segment seven narrowly triangular. Male first 

 pleopod cylindrical, gradually tapering and curving toward tip; tip 

 consisting of a fleshy lobe sharply bent back and having the opening of 

 the sperm duct at one end, rather than in the middle. (See Plate T, 

 fig. 7) 



Material examined: 33 specimens from 25 stations, of which 10 are 

 in the Gulf of California. (See Table 68) From Redondo Point Light, 

 Magdalena Bay, Lower California, and Tortuga Island, Gulf of Cali- 

 fornia, Mexico, to Octavia Bay, Colombia, including the Revilla Gigedo 

 Islands. 



Measurements: Male specimen: length 12.3 mm, width 11.3 mm, 

 rostrum 2.2 mm, width 2.5 mm, cheliped 11.2 mm, chela 4.9 mm, dactyl 

 2.2 mm, height of palm 2.1 mm, ambulatory legs 8.2, 7.5, 6.5, and 5.8 

 mm, respectively. Largest specimen, female: length 14.8 mm, width 15.3 

 mm. (Note reversal of length-breadth proportion in the two sexes.) 



