PART 1 GARTH : PACIFIC OXYRHYNCHA 335 



Lissa aurivilliusi Rathbun 

 Plate T, Fig. 8; Plate 33, Fig. 4 



Lissa aurivilliusi Rathbun, 1898, p. 575, pi. 41, fig. 4; 1902b, p. 284; 

 1910, p. 573; 1925, p. 333, pi. 246, fig. 2. Boone, 1927, p. 148, 

 fig. 44. Crane, 1937, p. 59. Garth, 1946, p. 384, pi. 65, figs. 3, 4. 



Type: Male holotype, U.S.N.M. No. 21575, length 12.5 mm, width 

 13 mm. 



Type locality: Off Cape San Lucas, Lower California, Mexico, 31 

 fathoms, Albatross station 2829. 



Localities subsequently reported, with collectors: Mexico: Lower 

 California: Magdalena Bay, 12 fathoms, Albatross (Rathbun, 1898); 

 Gulf of California: Arena Bank, 35 fathoms, Zaca (Crane). Galapagos 

 Islands: Tagus Cove, Albemarle Island, reef, Hopkins-Stanford Expe- 

 dition (Rathbun, 1902b) ; Charles, Indefatigable, James, Albemarle, and 

 Hood Islands, 3-70 fathoms, Velero III (Garth). 



Atlantic analogue: Lissa bicarinata Aurivillius. 



Diagnosis: A compressed branchial ridge extending without inter- 

 ruption from gastric prominence to postlateral angle. Posterior margin 

 biconcave, median projection angular. First three pairs of ambulatory 

 legs with single-crested carpi. Male first pleopod terminating in a trian- 

 gle in which the opening of the sperm duct is centered. 



Description: Surface everywhere microscopically punctate and short- 

 pubescent, hooked hairs confined to well-defined tracts, two rostral, two 

 protogastric, and two hepatic. Carapace with two prominent median 

 elevations, the smaller cardiac, the larger gastric ; from the latter a low, 

 compressed, granulate ridge extending obliquely to the postlateral angle. 

 Rostrum deflexed, broad at base, flaring toward extremities, each tipped 

 with a tubercle; median emargination shallow. Preorbital tooth acute, 

 incurving; postorbital cup sufficient only to conceal the fully retracted 

 eye ; two closed fissures trending obliquely inward, one superior and one 

 inferior. Anterolateral margins with an acute tooth at hepatic level and 

 another at branchial level, forming, together with the lateral angle of 

 the carapace and the postlateral tubercle terminating the diagonal ridge, 

 a tridentate projection affording concealment of the ambulatory legs in 

 a manner reminiscent of certain Parthenopidae. Posterior margin a 

 doubly concave arc interrupted by the acute median projection. 



Basal antennal article broad, granulate, outer portion forming floor 

 of orbit, inner portion giving rise to the minute flagellum, reaching not 

 more than half way to the tip of the rostrum. External maxillipeds pre- 



