No. 7 
REPORT ON THE CRUSTACEA COLLECTED ON THE SURVEY. 
By J. Gr. COOPER, M. D. 
CLASS CRUSTACEA. 
Order DECAPODA BRACHYURA. —Short-tailed Crustaceans. 
CANCER MAGISTER, Dana. 
The Great Western Crab. 
Cancer magister, Dana, TJ. S. Expl. Exped., Crust., 151, pi. vii, fig. 1.— Stimpson, Proc. Cal. Acad. Nat. Sc. 
I, 88.— Ibid. Journ. Bost. Soc. Nat. Hist. VI, 1857, (extracted, p. 18.) 
Cancer inorratus, Randall, Proc. Cal. Acad. Nat. Sc. (non Say.) 
Sp. Ch. —The largest crab of our Pacific coast; antero-lateral margin ten-toothed ; teeth anteriorly but little prominent. 
Third article of outer maxillipeds somewhat granulated, with the exterior apex broadly truncated. Feet of second pair 
longest, as long as the width of carapax. Length when full grown, nearly five inches ; width nearly nine. Color, light 
reddish brown above, darkest anteriorly, often light orange below ; inner sides of anterior feet and hands, crimson. 
This large crab is very abundant at Shoalwater bay during spring and summer. They can 
be taken by hand in large numbers at low tide on the sand flats or in shallow pools. Their 
spawn is deposited in July, after which they leave the bays for deep water. As food they are 
superior to the common crab of the Atlantic coast, (Lupa dicantlia.) 
PINNIXA FABA, Stimpson. 
The Parasitic IiUtraria Crab. 
Pinnothera faba, Dana, U. S. Expl. Exped. Crust. I, 381, pi. xxiv, fig. 4. 
Pinnixa faba , Stimp. Journ. Bost. Soc. Nat. Ilist. VI, (extracted, p. 30.) 
Sp. Ch. —The male resembles P. cylindrica , (Pinnothera cylindrica, Say,) and is much smaller than the female, while tho 
carapax is shorter and broader, its length being in the proportion of 1 to 1. 8. Length, 0. 36 inch ; breadth, 0. 65. Female, 
length, 0. 69 inch; breadth, 1. 05. Hands very large, finger more curved in the male than the female. Color, (living,) 
grayish white. 
This little crab is found within the large shell of the Lutraria , one of the 11 Clams’ ’ abundant 
at Shoalwater bay, but I never met with more than half a dozen in hundreds of shells. It 
probably lives on food brought into the shell by the current of water, and does not at all 
incommode its hospitable host. I never met with it in other shells. 
