PART 1 GARTH : PACIFIC OXYRHYNCH A 315 



compressed for overriding one another, bearing stout spines on their 

 anterior borders, ranging in number from ten on the first to five on the 

 fourth, a distal inferior spine on the first only, inferior spines on the 

 balance reduced to granules ; carpi doubly grooved ; propodi elongate and 

 narrowly cylindrical, dactyli short only in proportion to propodi, tips 

 corneous, strongly curving. 



Male abdomen with seven free segments, broadest between second 

 and third segments, tapering gradually from third to last segment, tip 

 narrowly rounded. 



Tip of male first pleopod tapering to extremity, arching to protect a 

 soft flap of tissue concealing the irregular opening of the sperm duct. 

 (See Plate S, figs. 3, 4, 6) 



Cheliped of adult male more massive than ambulatory legs ; merus 

 trigonal, armed with six stout spines along superior border and a seventh 

 at distal end ; carpus smooth ; manus smooth, inflated, dactylus occupying 

 two-fifths of its superior length, curving strongly to meet pollex at cren- 

 ulate tip, a strong, molariform tooth in gape, simple tooth of pollex 

 advancing into distal hiatus, inner margins excavate and sparsely setose. 



Notes on two males from Cocos Island, Costa Rica, stations 773-38 

 and 778-38: As compared to Herbstia tumida from the adjacent main- 

 land, the insular specimens differ in the following minor points: The 

 first of two interorbital spines is scarcely apparent. There are but six 

 instead of eight anterior marginal spines on the merus of the cheliped, 

 and the external meral spine is lacking. The outer pair of the four ante- 

 rior gastric spines is more prominent. The spinulosity is more apparent 

 throughout, but particularly on the posterior margins of the ambulatory 

 legs. There is a slight difference in the male first pleopod. Although 

 some endemism is to be expected in insular localities, the differences noted 

 are so slight as to be unworthy of so much as subspecific recognition, 

 particularly when some of them at least may be attributed to the small 

 size of the specimens (5.8 mm) and to the depth from which they were 

 recovered (30-50 fathoms). Plate R is of a Cocos Island specimen. 



Material examined: 31 specimens from 12 Velero HI stations. (See 

 Table 64) From Port Culebra, Costa Rica, to Santa Elena Bay, Ecua- 

 dor; Clarion and Cocos Islands. In addition to the above, 12 specimens 

 from 3 Askoy stations. (Garth, 1948, p. 27) 



Measurements: Male: length 8.9 mm, width 7.1 mm, rostrum 0.8 

 mm, width 1.1 mm, cheliped 9.5 mm, chela 4.8 mm, dactyl 1.9 mm, 

 height of palm 1.2 mm, ambulatory legs ca. 11.5, 10.8, 10.0, and 8.0 

 mm, respectively. Female: length 8.6 mm, width 7.0 mm. 



