420 MEMOIRS OF THE CARNEGIE MUSEUM 



I have repeatedly observed the digging and the renio\'al of the dirt out of the 

 burrow. Of course it is impossil:)le to see tlie digging going on in the field inside of 

 the l;)urrow, and consequently this was observed in the laborator3^ in the case of speci- 

 mens of G. diogenes and moncntgaknsis kept in captivity in large glass jars partly filled 

 with clay and water. It is not difficult at all to see them at work, and after they have 

 been brought into the laboratory the specimens begin to work within a short time, 

 digging out the mud, carrying it upward and plastei-ing it all over the walls of the 

 jar. After some time (days or weeks), their activity lessens, and not much digging 

 is done, producing the impression that the}' have become discouraged in the effort 

 to construct something similar to the burrows in the field. 



In digging the chehe of the first pereiopods are used. The fingers are slightly 

 spread out, so that they are al)0ut parallel, thus acting as forks for digging. They 

 are pushed vertically down into the mud on both sides at the same time, and a 

 lump of mud is thus loosened and lifted upward toward the ventral face of the 

 body. In lifting the chelipeds are bent toward the body (the region of the mouth), 

 and finally the ball of mud is appressed to the anterior part of the body and held 

 in position by the chelas. Very likely also the third maxillipeds take hold of it, 

 but it was impossible to ascertain this. In this position, as Goodman expres.ses it, 

 carrying an "armful " of dirt (or rather twoarmfuls), the crawfish walks slowly and 

 deliberately to the mouth of the hole. I have repeatedly observed it coming out in 

 nature.'' It advances to the top of the chimney and deposits the mud pellet upon 

 the rim, finally jjushing it into the proper position with the upper (outer) surface 

 of the claws. This latter act ajiparently was seen b}' Mr. J. DeP). Abl)Ott; but 

 according to my experience the mud is not Ijrought up upon the back of the claw, 

 but held, as described above, between the folded claws and the anterior part of 

 the body. 



After luivinc; Ijeen disturl)ed in the field, the crawfishes often begin to woi'k again 

 within a short time, and it is chiefiy on such occasions that I have seem them at 

 work, with the excepti(jn t>f one case, when I saw a large male of C. dhxiciiex at work 

 on the evening of Aj)i-il .30, 1905, (Hunday), in Nine-]\Iile Run, Pittsburgli. TIk- 



the " lateral tail-fins and telsoii " in any way. as suspected by .Sluifeldt ( 189(5), in the sealing up of the orilice of the 

 burrow, is hardly possible. 



" The following particular instances maybe mentioned: C. baiinni in a spring near Burgettstown, Washington 

 County, Aug. 4, 1904 ; C. cnroliiius at Indian Creek, Fayette County, July 11, 19i)4 ; at Ohiopyle, Fayette County, 

 July 12, 1904 ; at Myersdale, -Somerset County, August 11, 1904 ; C. uKinniigdliiisis in Fern Hollow, Pittsburgh, May 6, 

 1901 ; at Edgewood Park, Allegheny County, May 9 and 31, 1004 ; April '21, 190,5 ; Mon.ica, Beaver County, June 150, 

 1904 ; at Cheat Haven, Fayette County, September 6, 1904 ; at Cameron, Marshall County, W. Va., May 1, 190.") ; at 

 Morgantown, W. V., May 16, 190.5 ; C. diogenes at Dunbar, Fayette County, September 7, 1904 ; in Nine-Mile Run, 

 Pittsburgh, April 30, 1905. 



