of tlie West Coast of North America. 401 



margin denticulate, sometimes spinous (a young specimen has 

 a row of six or seven spines). 



kSurface of chelipeds covered with squamose ridges with a 

 crenulate edge, and thickly pubescent. The longitudinal 

 ridge on the carpus is formed of prominent oblique squamfe, 

 and that of the manus of a row of longitudinal crenulate squa- 

 mose teeth, passing into a line of tubercles down the centre of 

 the dactylus, which has a beaded upper margin. Fingers 

 closely fitting, hooked at the tip. Chelipeds equal. 



Meros of ambulatory feet with a row of spines, hidden 

 among long setge, on the anterior border, and a spine at distal 

 end posteriorly on the second and third pairs ; a slender spine 

 at posterior distal end of propodus. Last three joints of these 

 feet with long hairs and traces of colour (blue and red) ; 

 meros pubescent. 



Mulege Bay, Gulf of California. 



Petrolisthes {Pisosoma) sinuimanus, nov. sp. 



Carapax almost orbicular, somewhat convex, punctate, be- 

 coming granular on the lateral margins ; front sinuous in three 

 low lobes, the centre one very small, the preorbitals very long 

 and low ; sulci enclosing the gastric and cardiac regions dis- 

 tinct in young specimens, which have the carapax smooth. 



Eyes very small ; extenial antennae very short, scarcely as 

 long as the carapax. 



Chelipeds equal, similar. Meros usually with a blunt lobe 

 at its anterior distal end ; carpus nearly twice as long as wide, 

 usually with a single blunt tooth in the centre of its anterior 

 margin ; manus and dactylus forming an -obtuse triangle, outer 

 edge of manus and pollex serrated. 



Upper surface of the carpus and manus with three longitu- 

 dinal rolling ridges, divided by furrows equal to them in size, 

 the entire upper surface of meros, carpus, and manus deeply 

 punctate and granular; dactyli granular. Fingers hooked and 

 crossing at the tip. 



Ambulatory feet stout, punctate, the two anterior pairs with 

 the posterior distal end of the carpus produced backwards. 



Entire surface free from tomentosity or hairs, except two or 

 three stout hairs on the underside of the dactyli of the am- 

 bulatory feet. 



Length of carapax of largest specimen 5*5 millims., width 

 of ditto 5'5. 



Several specimens found under coral and stones at low 

 tide at La Paz and Port Escondido, Gulf of California. 



This species varies considerably : some few specimens are 

 without a trace of the lobe upon the meros or of the tootli upon 



Ann. & Mag. N. Hist. Ser. 5. Vol. ii. 27 



