HIGHER CRUSTACEA OF NEW YORK CITY 125 



without its representatives, modified to suit the conditions. Minute 

 forms belonging to the lower orders swarm at the surface of the 

 ocean and together with the young of the higher orders, form an 

 important supply of food for fishes and other animals. Other 

 similar species inhabit fresh water, and no roadside pool is without 

 them. Crawling over the bottoms of the bays and sounds, or buried 

 in the sand or mud, other varieties, usually larger and belonging to 

 the higher orders, may be found, while along the shores, under 

 stones or heaps of debris or rockweed, or living among the algae 

 on piles, or even in the piles themselves, are many others. 



Some also have been modified for a terrestrial life and may even 

 be said to have become domesticated; for certain of the sow-bugs 

 are rarely to be found except in the vicinity of human habitations. 



A few of 'the leading forms have been made use of directly as 

 food, but the economic importance of the group as a whole is mainly 

 indirect. 



The literature of the group is very extensive and dates back to 

 early times, though the early papers were of but little importance. 

 Even as late as 1840 it was still possible for Milne-Edwards to write 

 a Histoire naturelle des Crustaces and tell practically all that was 

 known concerning them, but the group has now grown far beyond 

 such bounds and most of the works deal with orders or smaller 

 groups. Consequently the greater part of the literature had best be 

 given under the heads of the different orders, but the following 

 general works may be mentioned here. 



De Kay, J. E. Zoology of New York. pt6 Crustacea. Alb. 1844. 

 Milne-Edwards, A. Histoire naturelle des Crustaces. Par. 1834-40. 

 Rathbun, R. Fisheries and Fishery Industries of the United States. 

 Sec. i, pt5. Wash. 1884. 



Economic and food values of Crustacea. 



Sars, Gr. 0. An Account of the Crustacea of Norway. Christiania 

 and Copenhagen. 1895 . 



Diagnoses of families etc., with short descriptions and figures of the species ; not yet completed. 



Say, Thomas. An Account of the Crustacea of the United States. 

 Acad. Nat. Sci. Phila. Jour. 1817-18. v.i. 



The first important work on American Crustacea. Gives first descriptions of many common 

 forms. 



