412 MEMOIRS OF THE CARNEGIE MUSEUM 



makes holes in the l^anks of streams. Faxon (l(S85a, p. 89 j reports that Mr. Uhler 

 found this species near Cumberland, Md., in " holes in the bottom and sides of a 

 canal," but whetlier these were made by the crawfish, or were cracks and joints 

 between stones, remains doubtful. In the lowkmds in Maryland this species, 

 according to tlie same authority, is found under stones in rivers and creeks. We 

 may say of (J. limosus that it is of all the species of this state tlie one which most 

 decidedly prefers the quieter water of large rivers, canals, and jionds ; that it 

 likes to hide under stones, but is not at all averse io muddy Ijottoms and masses of 

 vegetation. 



The latter trait distinguishes it from the species of the western rivers, CamJxtras 

 obscurus, which dislikes muddy bottoms (without stones) and vegetation. In fact, 

 this is so general a rule, that it is vain to look for ('. ohscurns in any part of a river 

 which has no stones. Only in rare and exceptional cases have I found it not hiding 

 under stones, apparently' being forced to do so by necessity. I observed this in two 

 cases : in the Allegheny River at Larabee, iMcKean ('ounty, and the Shenango 

 River at Linesville, C'rawford County. In both cases the river runs through peaty 

 soil (through the Pymatuning Swamp at Linesville), and it was only after a long 

 search that the s{)ecies was discovered, when I struck jjlaces where stones were lying 

 in the watei-. But it was interesting to note that at l)Oth places the supply of stones 

 was apparentl}' not sufticicnt to accommodate all the specimens, and so a number 

 of them had to be content with a shelter atlbi'ded by the peaty banks, where they 

 had built short, hoiizontal holes, not more than a few inches long, clo.se to the edge 

 of the water. These holes are apjiarently only temporary, and are often abandoned 

 and changed, since a number of them were seen on the banks above the present 

 water level, which wei-e built and iidiabited at a previous higher stage of the river. 

 ('. obscurus does not love vegetation. The patches of iJiaidhera americaua, so fre- 

 quent in our rivers, do not harbour many crawfishes, although they are not entirely 

 absent from them ; but the}' do not hide undei' these plants and their roots, but 

 under stones. They always scoop out a hollow under the stone selected, and bring 

 out the mud and gravel, throwing up a small rul)l)ish pile in front of the hole, 

 which, however, is soon obliterated by the current. The crawfishes ai'e easily found 

 bs' noting these rubbish piles. They rarely go into deep water (possibly only in 

 winter), but always are close to the banks in shallow water; liut on the other hand 

 they never go out of water. In the mountains of western Pennsylvania this species 

 is generally absent, and it is appai'ently the roughness of the streams which causes 

 its disappearance. The stones, under which it hides, must be rather permanent in 

 their position, and must rest upon a bed of mud, sand, or gravel, to afford congenial 



