Occasional Papers of tlic Musciiin of Zoology 3 



ground water level is above the hard pan and it is only neces- 

 sary for the crayfish to extend their burrows into the subsoil 

 to insure a constant supi^ly of water. 



The old burrows occupied by crayfish were entirely without 

 chimneys, and were approximately round at the entrance, which 

 had a diameter of about three inches. The entrance was more 

 or less overhung with grass and at one side was a small bare 

 space about six inches in diameter. These bare "platforms'' 

 are evidently the result of the activities of the crayfish in 

 cleaning out the burrows. The mud that is brought up is more 

 or less fluid and in the case of the old l)urrows is deposited only 

 occasionally and in small quantities. The mud impedes the 

 growth of grass and serves to keep the earth at the front of 

 the entrance free from vegetation. Immediately inside the en- 

 trance the burrows slanted obliquely downward for a few 

 inches and then became nearly perpendicular for the rest of the 

 depth, three feet or more, and the walls were slightlv rough- 

 ened. It is to be presumed that the l)urrows always extended 

 to water but this could not be verified in some cases. 



The burrows occupied by frogs (PI. Ill) differed but slight- 

 ly from those just described. Hurter says of the burrows inhab- 

 ited by frogs, "The inhabited holes are easily recognized as the 

 entrance as well as a little platform in front of it is worn 

 smooth." Our observations did not bear out this statement. 

 We were quite unable to distinguish by external appearance 

 the old holes occupied by crayfish from those inhabited by 

 frogs. The openings were of approximately equal size and 

 overhung with grass, and the platforms were nearly always 

 present (PI. II, Fig. 2). Only rarely was an old hole found 

 without a platform and in such cases when dug out it was found 

 to be either entirely abandoned or to contain a crayfish. On the 

 other hand many holes with well-developed platforms contained 



