SYNOPSES OF NORTH-AMERICAN 
INVERTEBRATES. 
VI. Tue ASTACIDÆ OF NORTH AMERICA. 
W. P. HAY. 
Tue following synopsis of the genera Astacus and Cambarus 
will be found to include all the valid species reported from the 
whole continent of North America. 
The crayfishes, our largest and most conspicuous fresh-water 
crustaceans, are well known to every student of animal morphol- 
ogy. They occur in abundance in most lakes and streams, and, 
with the exception of the New England States and the Great 
Plains region, most localities will be found to support several 
species. They are especially abundant, individually and as species, 
in the southern and central portions of the United States. 
In form, size, armature, color, and habits there is the 
greatest variation among the seventy-nine species and sub- 
species now recognized in the genus Cambarus and the five 
known species of Astacus. Moreover, almost every species is 
liable to show the most perplexing variations beyond those 
depending upon age and sex. On this account the identifica- 
tion of many species becomes exceedingly difficult, and in some 
cases is possible only when a set of type specimens is at hand. 
It is thought, however, that a careful use of the synopses given 
will enable even a beginner to identify with accuracy all but the 
most puzzling species. In the first list the natural groups are 
given with the ch ters disti hing them, and the geographi- 
cal distribution of each species is is roughly indicated. The second 
list is a purely artificial key, based upon trenchant characters, by 
which any specimen, male or female, may be identified. 
The most important papers on North American Astacidz are : 
1. HARLAN, R. Trans. Amer. Philos. Soc. Philadelphia. Vol. iii, Dp. 464: ~ 
1830. 
2. TELLKAMPF, T. /. Muellers Archiv, p. 383. 1844. “ 
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