PART 1 GARTH ! PACIFIC OXYRHYNCHA 449 



Diagnosis: Lateral margins broadly arcuate. Angle of deflection of 

 rostrum less than 90°. Dorsal tubercles prominent, erect, interspaces not 

 deeply excavate. Chelipeds convex above, surface between crests tubercu- 

 late. Three paired sternal spines obsolescent. Ambulatory legs not conspic- 

 uously crested. Male first pleopod truncate, a tuft of long golden hairs 

 terminally crossing midline to mesh with those of opposite pair. 



Description: Carapace broader than long, dorsum of irregular relief 

 with high tubercles and shallow depressions alternating. Anterolateral 

 margins continuous with posterolateral, together forming a broad arc 

 terminating in a strong spine at the end of the branchial ridge. Front 

 triangular, minutely tridentate, and moderately deflexed, the angle 

 formed with the general gastrocardiac level being somewhat less than a 

 right angle. Two thickened supraorbital ridges separated by a shallow 

 median sulcus. Gastric region high, surmounted by an anterior pair of 

 tubercles and a smaller posterior median tubercle. Cardiac region con- 

 sisting of a single raised tubercle well isolated from gastric and bran- 

 chial regions by depressed areas similar to those of P. (P.) excavate 

 but not so deep and appearing to be more nearly confluent with one 

 another anteriorly as well as extending posteriorly to the margins of the 

 carapace. Branchial regions high, swollen, separated anteriorly from 

 hepatic regions by an oblique groove and posteriorly from the postlateral 

 spine by a slight sulcus, each bearing a posterior tubercle in addition to 

 the postlateral spine. Hepatic region with a subacute tooth, the outer 

 margin making a near right angle with the anterior branchial margin 

 and together with it outlining a depressed area second only to that of 

 the dorsal portion of the carapace in size. Posterior margins small toothed 

 except for a slightly larger tooth closer to the postlateral spine than to 

 the midline. (P. (P.) excavata has two, equally spaced.) 



Basal article of antennules broad, anteriorly rimmed. First free an- 

 tennal segment lodged in orbital hiatus. External maxillipeds granulate 

 and tuberculate, merus broadly produced at outer angle to conceal end 

 of exognath, interiorly notched to receive 3-jointed palpus, the first 

 article of palpus compressed in a plane nearly perpendicular to that of 

 the merus. Sternum smooth and almost devoid of tubercles anteriorly; 

 posterior to the chelipeds the three spines in a row noticeable in P. (P.) 

 excavata present as inconspicuous tubercles. 



Chelipeds longer than those of P. (P.) excavata, yet compatible with 

 the subgenus. Merus with three tuberculate spines on inner and three 

 on outer margins, between the former accessory spines, three berried 

 tubercles, the distal the largest, in an oblique row. Carpus irregularly 



