PART 1 GARTH : PACIFIC OXYRHYNCHA 453 



lateral angle strongly obtuse, margin sub-entire, hepatic region rounded, 

 prominent. Larger depressions as follows: a deep hollow between orbits 

 continued backward as a shallow sulcus on the nasogastric region, a 

 deep depression at each inner branchial angle, and a less profound linear 

 furrow on either side of the small, isolated cardiac region. Between these 

 depressions the reticulating ridges smooth, consisting of rounded tuber- 

 cles covered with depressed granules. Rostrum rounded in dorsal view, 

 produced downward at the middle as a smaller lobe approximating the 

 inter-antennular septum. Orbits small, circular. Anterointernal angle 

 of basal antennal article not reaching front. A row of six or seven acute 

 tubercles on endognath of external maxilliped, the posterior tubercle 

 much the largest. Sternum without a large spine at base of cheliped, and 

 in the male deeply hollowed in front of abdomen. 



Protuberances of cheliped, except those of dactylus, rounded lobes or 

 tubercles. Arm short and stout proximally; the largest tubercles the one 

 near distal end of outer-upper border, and one near proximal end of 

 inner-lower border. Of the tubercles on the manus, the middle one of 

 the upper row by far the largest. Fingers short, stout, curving inward, 

 and gaping in the large cheliped ; dactylus armed on inner surface with 

 three or four small spines or sharp-pointed tubercles. Lower border of 

 propodus armed with six triangular, acute teeth. Legs with surface only 

 slightly rough save on dactylus; marginal prominences either lobes or 

 tubercles except on lower edge of propodus and on dactylus, there sharp 

 denticles. (Rathbun, modified and revised to eliminate the comparative 

 references to Thyrolambrus astroides) 



The sternal pit, not mentioned in the original description, but clearly 

 shown in Rathbun's figure of a male specimen (1925, pi. 197, fig. 2), 

 is often present in the female, concealed by the more extensive abdomen, 

 as a double pit or series of small pits. 



Material examined: 38 specimens from 22 stations. (See Table 99) 

 From Magdalena Bay, Lower California, and E of San Marcos Island, 

 Gulf of California, Mexico, to Gorgona Island, Colombia, including 

 Clarion Island of the Revilla Gigedo Islands. 



Measurements: Largest specimen, female: length 15.9 mm, branchial 

 width 20.7 mm, hepatic width 14.3 mm, exorbital width 5.9 mm, cheli- 

 ped 21.3 mm, merus 6.3 mm, manus 9.8 mm, dactylus 5.4 mm, height 

 of palm 5.4 mm. Male specimen: length 14.1 mm, branchial width 18.9 

 mm, hepatic width 11.6 mm, exorbital width 5.8 mm, cheliped 28.7 

 mm, merus 8.3 mm, manus 13.4 mm, dactylus 6.7 mm, height of palm 

 8.1 mm. 



