OHAPTEE IV. 



CRAYFISH AXD CRABS. 



[Crustacea.) 



RAYFISB and Crabs belong to that very interesting 

 Class of the Animal Kingdom known as the Crustacea, 

 being arrayed in the Subkingdom Annulosa, created 

 to contain the more or less nearly allied groups of the 

 insects (Insecta), the myriapods (Myriapoda), and the spiders 

 with their kin (Arachnida). In a more restricted sense they form 

 the division Arthropoda, or the Articulata of some naturalists. 

 In this country a great many kinds of them occur in its fauna, as 

 all the various species and subspecies of crabs, lobsters, cray- 

 fish, king-crabs (Limulus), water-fleas, besides a perfect legion 

 of others, to which no common names have been given, and a 

 host of fossil forms, such as the trilobites and their allies. 



There is a very voluminous and helpful literature extant upon 

 the biology of the Crustacea, the published labors of many able 

 minds. One of the most useful books known to me on the subject 

 is Huxley's " Crayfish," and it will give the student a very clear 

 idea of the anatomy and natural history of one of the best known 

 members of this group. 



Fully examined in a comparative way in connection with the 

 typical allied forms, the lobsters and crabs, the crayfish will lead 

 to a general knowledge of the Class, and a good understanding 

 of the habits and characters of the widely varying forms repre- 

 senting the many different orders of the Annulosa, apart from 

 the insects, spiders, and myriapods. 



Our United States crayfish belong to two well-marked genera, 

 Canxbarus and Astacus, the first being divided into five groups, 

 and the latter genus all being contained in a single group. The 

 most able and thorough work upon them known to me is " A Re- 

 vision of the Astacida\" of which Mr. Walter Faxon, of Harvard 

 College, is the author. This fine quarto memoir gives a very com- 

 plete account of all the crayfish of this country known to science 

 up to the time of its appearance (August. 1885). Another Ameri- 

 can naturalist, Professor A. S. Packard, of Brown University, has 

 also powerfully advanced our knowledge of these forms by his 

 numerous contributions to the subject, not to mention those of 



