1921] Schmitt: The Marine Decapod Crustacea of Califorma 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) scaled 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.—Reddish (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 sealed. 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 
