SYNOPSES OF NORTH-AMERICAN 
INVERTEBRATES. 
J. S. KINGSLEY. 
IV. AsTACOID AND THALASSINOID CRUSTACEA. 
Tune following synopsis, together with the one given in this 
journal for September, includes the whole macrurous fauna of 
North America north of the southern boundary of the United 
States and within the hundred-fathom line. Geographical dis- 
tribution is indicated, as before, by full-faced letters : N, M, S, 
indicating the northern, middle, and southern Atlantic coast ; 
A, P, D, corresponding divisions of the Pacific coast. 
The Astacoid forms include those forms familiarly known 
as lobsters and crayfishes, as well as some others for which 
no common name is in general use. The crayfishes (genera 
Astacus and Cambarus) are inhabitants of fresh water; the 
others are marine. Most important of these is the lobster, 
once very abundant from New York northward, but now 
becoming much more rare, owing to overfishing and to dis- 
regard of the law prohibiting the taking of immature and 
egg-bearing animals. 
The crayfish are fresh-water forms, occurring sparingly in 
New England and the southern British Provinces, and far more 
abundantly in the rest of our territory, where every stream and 
pond has its representatives. The discrimination of the species 
is not easy, and for the present we give no key to the fifty-one 
species described from our limits. The difficulties which sur- 
round the systematic arrangement of these forms can be 
seen from the fact that the late William Stimpson, our most 
accurate student of the Crustacea, would not touch the crayfish, 
remarking that either we had only one species of Cambarus in 
our country, or each mud puddle had its own species. 
In the southern waters and on our Pacific coast the lobster 
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