OF THE UNITED STATES 55 



the late Professor Cope, and of Dr. C. C. Abbott, F. W. Putnam, 

 H. A. Hagen, S. I. Smith, W. F. Bundy, S. A. Forbes, Ralph S. 

 Tarr, and W. P. Hay. There are upward of a hundred different 

 kinds of crayfish in the United States, and new forms of them 

 are constantly coming to our knowledge. In the U. S. National 

 Museum, the crayfish and crabs are being best studied by Mr. 

 James E. Benedict, Mr. Eichard Rathbun, and Miss^Mary Rath- 

 bun, and there is a large store of material illustrating this group 

 in the collections of that institution. 



The general form and appearance of a crayfish is so well known 

 that no special description of one is here necessary, while in a 

 brief chapter it is not possible to enter upon the highly instruct- 

 ive subject of the anatomy of these animals. One should turn 

 to Professor Huxley's book for that, where it is given in great 

 detail. Of our common forms, the ones best known to me are 

 Cambarus diogenes and C. bartonii robusta. The first-named I had 

 many opportunities to study in Louisiana, while collecting in that 

 State many years ago, while Barton's crayfish I found in the 

 country districts about the City of Washington, D. C. Both of 

 these species are builders of the so-called "chimneys," struc- 

 tures that have given rise to no little amount of speculation as 

 to their object and use. Many of these chimneys, constructed by 

 C. diogenes, I found in the low, flat meadows, south of the city 

 of New Orleans. Here they were usually built up vertically, 

 even where they stood on the sloping banks of the ditches, and in 

 many instances the taller ones were seen to have the apertures 

 at their tops sealed over, and this condition obtained still more 

 commonly among those of lesser stature. The sub-cylindrical 

 passage used by the owner of one of these " chimneys " traversed 

 its entire length, and down into the ground a varying distance 

 below the level of the latter. When very low, one of these affairs 

 reminded me more of a mound of mud, particularly when it was 

 sealed over at its entrance, but after being carried up to a greater 

 height, and especially when they were open at the top, perhaps 

 they did appear as much like little earthen chimneys of cylindri- 

 cal form as anything else. Where the ground was dry the method 

 of construction could easily be observed, for they were evidently 

 built up of small pellets of mud laid on in a single course, while 

 at the bottom, by the pellets rolling down, a mound-like base 

 was formed, around the outer boundary of which numerous loose 

 pellets were scattered about. Where the ground was very wet 



