818 NATUBAL HISTOET OF AQUATIC ANIMALS. 



Francisco markets, although comprising no inconsiderable part of the total catch of Shrimp, and 

 at some seasons it is more common thaii its congener. The average length of the specimens 

 taken on the Pacific coast is said to be about two and a quarter inches, but large examples 

 exceed three inches in length. This form, which is a sort of color variety, is easily distinguished 

 from C. franciscorum by its black tail, and the large proportion of black upon its body, as well as 

 by the different form of the hand, the movable finger of which is much shorter and folds trans- 

 versely across the tip of the hand. From its black coloring it has received the name of " Black- 

 tailed Crab." 



This Shrimp is taken on the west coast in connection with C.franciscorum, and is sold fresh in 

 the markets as well as boiled and dried' for exportation to China. 



THE CALIFORNIA SHEIMP CRANGON FRANCISCORTJM, Stimpson. 



According to notes furnished by W. N. Lockiugton, this is the largest species of Shrimp on 

 the Pacific coast of the United States, and is the Shrimp par excellence of the San Francisco mar- 

 kets, where large quantities are sold during nearly every month of the year. 



The total length of the body, in the adults, ranges from three to three and a half inches, 

 while in the same the length of the carapax is about seven-eighths of an inch. 



From the Pacific coast variety of Crangon vulgaris this species can be distinguished by its 

 larger size; by the absence of the black tail and large black spots, characteristic of the former; 

 by the small dots of dark tint which mottle the surface; and most readily by the much greater 

 length of the movable finger of the hand, which folds parallel with the side of the hand instead 

 of across its extremity. 



Crangon franciscorum has a somewhat limited range, not being known from north of Puget 

 Sound, nor south of Point- Conception, California. In San Francisco Bay and Tomales Bay it is 

 exceedingly abundant, frequenting especially the sandy coves along their shores. Not only is 

 this Shrimp largely consumed upon the coast when fresh, but it is also taken by the Chinese in 

 immense quantities and shipped to China after boiling and drying. The Shrimp industry affords 

 employment to a large number of Chinese, and Constitutes an important factor in the export trade 

 of San Francisco. The Shrimp are usually caught in purse-nets, which are conical in shape, 

 about twenty-five feet long and ten feet across the mouth ; they taper to the lower end, which is 

 opened and closed by means of a* "puckering string." It is said that no diminution in the number 

 of Shrimp results from the continuous fishing, although the edible species of fish are nearly 

 exterminated in San Francisco Bay. 



A species of Hippolite (H. brevirostris), of a uniform light crimson or scarlet color, occurs at 

 the Straits of Fuca, in San Francisco Bay, and probably along the intervening coast. In San 

 Francisco Bay it is taken with the Crangons for food. 



THE COMMON PRAWN PAL^IMONETES TULGAEIS, Stimpson. 



The common American Prawn, which closely resembles the English species, although occurring 

 in great abundance along some portions of our Atlantic coast, does not rank among our food 

 invertebrates on account of its small size. It frequently makes up for that deficiency, however, 

 by its great abundance. 



The average length of specimens is about one and one-half inches. The body is translucent, 

 almost colorless, but is " marked with irregular, ill-defiued, dark blotches and spots, which 

 admirably adapt it for concealment among the discolored and dead leaves of eel-grass, at or near 

 the bottom," in which localities it is most abundant. The American Prawn differs from the 



