1921] Schmitt: The Marine Decapod Crustacea of California 85 
a little more than twice as long as wide, with edges subparallel; the margin 
against which the dactylus closes more nearly transverse than longitudinal. Fifth 
segment of abdomen with a distinct median carina. 
Dimensions.—The specimens taken in San Francisco Bay ranged up to 58 mm. 
in length from tip of rostrum to end of telson; the greater number averaged 
between 30 and 35 mm. in length. 
Color.—A very dark gray, or blackish, becoming entirely black at the tail. 
Hands tinted with lilae (Stimpson). 
Type Locality —Tomales Bay, California. 
Distribution.—Acecording ‘to Holmes, who includes here C: alaskensis, this 
species ranges from Alaska to Lower California. I have seen specimens only from 
Comox, British Columbia, southward (Rathbun). Japan (Balss). Littoral to 
31 fathoms. 
Biological Survey of San Francisco Bay—Except for Crago fran- 
ciscorum, C. nigricauda is the most abundant and widely distributed 
species found in the bay and as compared with that species, although 
taken at seven more dredging stations, was only obtained at about 
half as many, or 69 out of 137, hydrographic (tow-net) stations. 
Crago mgricauda was taken in the upper bay at 82% (18) of 
dredging and 22% (18) of the hydrographic stations; in the middle 
bay at 77% (56) of the dredging and 16% (18) of the hydrographic 
stations; in the lower bay at 50% (19) of the dredging and 31% 
(33) of the hydrographic stations; and outside at 538% (9) of the 
dredging stations only. 
A summary of these figures indicates that this species, although 
constituting one of the principal returns of the tow-net, is rather an 
inhabitant of the lower or bottom strata of water than of the upper 
layers. It was taken, in all, at three-fourths (75%) of the. total 
number of dredging stations, while it is recorded at less than a fourth 
(23%) of the total number of hydrographic (tow-net) stations, and 
of these only seven contained more than ten examples. 
With respect to the character of the bottom preferred, little choice 
is displayed. There seems to be a tendency for the greater number 
of specimens to frequent the more or less muddy bottoms rather than 
those of a harder composition, predominantly sand, gravel, or rock; 
but this indication is possibly the result of using a highly effective 
piece of apparatus on the former type of bottom and not on the latter, 
the so-called ‘‘sledge trawl’’ (Sumner, 1914, p. 5, and pl. 8). Of the 
twenty-seven dredging stations, which returned fifty or more speci- 
mens, 74% (20) were made with the sledge trawl. 
Although in the bay, i.e., Golden Gate, a considerable number of 
specimens were taken at stations having a maximum depth of 43 to 53 
fathoms (D 5808, 5809) and two possibly at 60 fathoms (D 5738, 
