1921 J Schmitt: The Marine Decapod Crustacea of California 181 



Petrolisthes gracilis Stimpson 



Plate 32, figure 4 



Petrolisthes gracilis Stimpson, Ann. Lye. Nat. Hist. N. Y., 7, 74, 1859 

 (1862) ; Lockington, Ann. Mag. Nat. Hist. (5), 2, 396, 1878. 



Characters. — Carpus of chelipeds long and narrow, about three times, or nearly 

 three times as long as wide, anterior and posterior margins subparallel; upper 

 surface very smooth, punctate, or at most very minutely and inconspicuously 

 (microscopically) sealed or tuberculated. Carapace smooth and flattened, though 

 distinctly areolated, minutely striated on branchial regions, tending to become 

 punctate elsewhere, never tuberculate. Merus of ambulatory legs not hairy. 



Dimensions. — Type: length of carapace 11.2 mm., width 10.4 mm. Of speci- 

 mens in the U. S. National Museum: length of carapace 10 to 15 mm., width 9.5 

 to 16 mm. 



Color. — Eeddish (Stimpson). 



Type Locality. — Guaymas, Mexico. 



Distribution. — Monterey, Santa Catalina Island, and Pacific Grove, California; 

 Guaymas, Mexico. 



Petrolisthes rathbunae Schmitt 



Plate 32, figure 3 



Petrolisthes rathbunae Schmitt (MS), Hilton, Jour. Ent. Zool., Pomona 

 Coll., 8, 72, fig. 6, 1916 (figure only, not specifically recognizable). 



Description. — Entire animal quite rough, scabrous. Carapace strongly striated 

 and rugose, rugae forming anteriorly directed scale-like projections and ridges, 

 more pronounced at anterior end of carapace. Lines between rugae on carapace 

 beset with short hairs, which are more thickly set on demarcation lines of areo- 

 lations. Dorsal surface of carapace generally flat, with broadly triangular rostral 

 process, sharply depressed from a line connecting the posterior margins of the 

 orbits. Second segment of antennal peduncle slightly more than the length of 

 the third, well scaled; segments of flagellum alternately furnished on lateral 

 margins with long and short hairs. Upper and lower surface of chelipeds covered 

 with squamiform tubercles, more prominent dorsally and on dorsal ridges. Carpus 

 two and one-third to two and one-half times as long as wide, edges practically 

 parallel, finely denticulated on anterior margin in adult; distinctly saw- toothed in 

 young specimens. Posterior and ventral surface of carpus and entire merus 

 covered with overlapping, scale-like rugae, which on carpus form a dorsal posterior 

 ridge no rougher than general surface of carpus, and which ends distally in a 

 tooth. The inner edge of the palm and outer edge of the movable finger are 

 similarly scaled. Ambulatory legs and plates of abdomen scaled, as well as carpus, 

 merus, and ischium of external maxillipeds. All joints of legs well beset with 

 hairs, both edges of abdominal segments fringed with hairs, closely set short 

 hairs interspersed with longer ones. Most hairy of west coast species of Petro- 

 listhes. 



Dimensions. — Type (Cat. No. 49176, U. S. N. M.), male: length of carapace 

 18 mm., width 17 mm., length of carpus of cheliped about 16 mm., width of carpus 

 6 mm.; of a female: length and width of carapace each 17 mm., length of carpus 

 of cheliped 14 mm., width of carpus 5 mm. 



Color. — A comparatively fresh specimen in formalin, received from Prof. 

 W. A. Hilton, has a general ground color of salmon, fading out to a paler, more 

 yellowish tint toward posterior edge of carapace, proximal portions of ambulatory 



