PART 1 GARTH : PACIFIC OXYRHYNCHA 477 



two rows in concavity of terminal portion, and marginally. Male second 

 pleopod little more than half the length of first, reflexed, corneous tip 

 marginally denticulate; a subterminal cluster of denticles. 



Description: Carapace broadly triangular; median region narrow, the 

 flattened upper surface bounded by two granulated ridges, converging 

 to a point behind. Cardiac region furnished with a three-sided, pyramidal 

 elevation, the edges usually granulated. Posterolateral regions large, and 

 furnished with an S-shaped, granulated crest, extending from near the 

 posterior end of the median region to the acute lateral angles of the 

 carapace; in front of the anterior bend of this crest a pair of minute 

 tubercles. Rostrum triangular, subacute, not depressed. Anterolateral 

 margins straight or slightly concave in front, convex near the middle, the 

 posterior portion passing outwards and backwards, arching over the legs ; 

 the teeth on the anterior part small and irregular, but becoming larger 

 posteriorly, there furnished with secondary denticles. Posterolateral mar- 

 gins transverse ; posterior margin not produced over the abdominal seg- 

 ments. . . . Ischium of the maxillipeds smooth, the anterointernal angle 

 produced ; merus small, the surface concave and bearing near the middle 

 a prominent tooth. 



Chelipeds long, trigonal ; the sides of the merus convex, the edge 

 sharply granulate to dentate; carpus with three or four granulate lines; 

 hand about as long as the merus, the angles prominent and dentate and 

 the sides concave ; pollex short, deflexed ; dactyl short, but longer than 

 the pollex, and when closed its outer margin nearly at right angles to the 

 long axis of the hand. Ambulatory legs compressed, strongly carinated 

 above; dactyls narrow, strongly sulcate, and corneous-tipped. (Holmes, 

 modified) 



A long triangular concave area extending from the subhepatic region 

 back to the afferent branchial openings, including the exognath and sur- 

 rounded by a fringe of hair ; outside this area, and above the ischium of 

 the cheliped, a raised, level, oval area against which the inner surface 

 of the manus plays, when the cheliped is flexed. (Rathbun, 1925, modi- 

 fied) 



Material examined: 922 specimens from 136 stations or localities. 

 (See Table 106) From Drakes Bay, Marin County, California, to 

 Dewey Channel, Lower California, Mexico, including all eight islands 

 of the Channel Islands group ; Gulf of California at Outer Gorda Bank. 



Measurements: Largest specimen, male: length 21.0 mm, width 34.0 

 mm, rostrum 1.2 mm, width 1.8 mm, exorbital width 5.0 mm, cheliped 



