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 daetylus 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 lilac (Stimpson). 



Type Locality. — Tomales Bay, California. 



Distribution. — According to Holme's, who includes here C. alaskensis, this 

 species ranges from Alaska to Lower California. I have seen specimens only from 

 Comox, British Columbia, southward (Bathbun). 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 nigricauda 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 53% (9) of the 

 dredging stations only. 



A summary of these figures indicates tbat 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 pi. 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, 



