PART 1 GARTH : PACIFIC OXYRHYNCHA 423 



teriorly a cluster of hooked hairs. Hepatic areas concave, margins 

 anteriorly converging, edges granulate, a prominent constriction between 

 hepatic and branchial regions. Branchial areas wide, relatively low, the 

 few tubercles arranged in patterns accentuating the relief. Three lateral 

 prominences, the median by far the largest, subacute, and located at the 

 widest portion of the carapace, the posterior similar but smaller, the 

 anterior little more than a tubercle. Carapace arching broadly posteri- 

 orly, intestinal region with a few clustered granules disposed trans- 

 versely. The cardiac region, although high, not encompassing any of the 

 branchial or intestinal area, as in Hemus analogus. 



Basal article of antenna broader than long, produced anteriorly and 

 externally to form a partial floor for the orbit ; orbit incomplete beneath. 

 External maxilliped slender, merus equaling ischium in length, narrow 

 proximally, broadening distally and outwardly into an arc forming the 

 anterior as well as the exterior border and extending well forward of 

 the insertion of the cylindrical, 3-segmented palp, each article of palp 

 bearing a medial, distal tuft of hair. Exognath of maxilliped, especially 

 basal portion, more robust than endognath. 



Chelipeds feeble in both sexes, tips of fingers incurving, denticulate, 

 with little or no gape. Walking legs robust, decreasing regularly in 

 length from first to fourth, the meri broadened above by means of a 

 granulate ridge and below by means of a lamellate projection, the edge 

 irregularly serrate and denticulate. Superior surfaces of lamellae slightly 

 concave and superficially smooth, not convex and ridged as in Hemus 

 analogus, with microscopic surfacing similar to that of the depressed 

 regions of the carapace. Each successive merus fitting snugly against the 

 preceding, that of the first leg conforming with the contour of the 

 hepatic margin. Carpi continuing above the granulate ridge and below 

 the denticulate lamella of the merus and carrying distally a protuberance 

 repeated medially on the longer and similarly ornamented propodi. 

 Dactyli stout and strongly curved, the tip of each with a corneous ridge 

 beneath in place of denticles. 



Male abdomen with seven free segments, the first three ornamented 

 with granules, broadest at segment three, last segment narrowly trian- 

 gular. Male first pleopod with a double lateral flange, opening terminal. 

 (See Plate Y, fig. 7) 



Material examined: 18 specimens from 16 stations. (See Table 90) 

 Although the species ranges from Angel de la Guarda Island, Gulf of 

 California, and Puerto San Carlos, Sonora, Mexico, to Santa Elena 

 Bay, Ecuador, including the Revilla Gigedo Islands, only specimens 

 from the type locality, Costa Rica, and from adjacent northern Panama 



