0I;TMANN: TUE crawfishes of the state of PENNSYLVANrA 419 



from the surface. The holes are driven clown by the crawfish to such a depth that 

 a good supply of water is at the bottona at all seasons. Where the water appears at 

 the surface, or is very near to it, the holes are sometimes hardly a foot deep. Gen- 

 erally they are considerably deeper, as much as two iind three feet. They certainly 

 at limes go even deeper than this, but I never tried to dig at places where such con- 

 ditions prevailed, that is to sa\', where from all appearances the level of the ground- 

 water was more than three feet from the surface. Such conditions were not infre- 

 quently met with in the case of C. carol inus. 



In a general way we ma}^ say that the holes of (\ bartoni are very simple 

 (PI. Xl>, Fig. 8; ri. XLI, Fig. 1). Among the true chimney-builders the holes 

 of C. diogenes are also rather simple, consisting often of a single shaft with a pocket 

 at the bottom (Pi. .\1J, llgs. 5 and 6). In C. monongalensis they are decidedly 

 more complex (PI. X Id, Fig. 2), and the highest degree of complexity is reached 

 in ('. carolinus (PI. XL, Fig. 9). 



The shape of the buri-ows of C. diogenes was first described by Girard (1852, p. 

 89), who called attention to their variable character. Tarr (1881, p. 127) has given 

 sketches of burrows of this species, and also observed their variability. Of C. caro- 

 liims, only the fact that it is a chimney-builder was known (Faxon, 1885«, p. 71). 

 The burrows of C. monongcdensis (as dubius) were described by \\'illiamson (1901, p. 

 12), and he emphasizes their complexity as compared with those of C. diogenes. 



c. Construction of the burrows and of the chimneys. 

 Although the "chimneys" or mud-piles at the mouths of the burrows have 

 often been descrii)ed and their purpose discussed, (Girard, 1852; Tarr, 1854; Shu- 

 feldt, 1896; Harris, 1903), the manner in which the crawfish excavates the burrow 

 and piles up the mud in front of it had never been correctly observed. Abbott 

 (1885) describes how Mr. J. DeB. Abbott saw the crawfish (C. diogenes) engaged in 

 building its chimney, and states that it comes out of its hole " bearing on the back 

 of its right claw a ball of clay mud, wliirli by a dexterous tilt of the claw was 

 placed on the rim of the chimney." This description, as we shall presently see, is 

 apparently founded upon correct observation, but the observer witnessed only the 

 final act, and drew from it a wrong inference. The old ob.servation of Goodman 

 (1833, (1842), p. 293), that C. bartoni brings out of its hole an "armful of rubbish 

 and throws it over the side of his cell, and down the stream." should be quoted, 

 since, although referring to another species, it is pertinent and applies well to the 

 regular chimney-builders as regards the mode of cairying the mud.'""' 



'■>Tlie way of carryinj; tlie niiul out of the holes seems to be identicnl in nil Imrrowiiig species. It has been ulaerved 

 in a similar form by Mr. W. S. Sutton in C. pilonus Hay, ns described by 1 larris ( 1900, p. 27->). That llie cniwlisli n.ws 



