HABITS OF CEAY FISHES. 815 



"It is difficult to say which of the three species is the most abundant in the general locality 

 we have named, inasmuch as they seem to prefer different streams ; one being a plant-loving, one 

 a stone-haunting, and the tMrd a mud-frequenting species. In their respective haunts each is 

 apparently as numerous as is either of the others in its chosen, home. . . . We have found 

 Gambarus acutus to frequent running streams which have masses of vegetation growing in them, 

 the animal in question resting upon the plants, usually near the surface of the water. We have 

 found since our collecting excursions, on carefully approaching clear running streams, such as 

 just mentioned, that this Cray-fish is to be seen resting on the plants, always with the head 

 directed down-streiam. If disturbed, they would dart backward, down to the roots, apparently, 

 of the plant upon which they were sitting. After a lapse of about ten minutes they would return 

 to their former resting place, creeping up the plant down which they had so suddenly darted tail 

 foremost. 



"The Cambarus affinis is apparently the river species of this locality. We have been able to 

 find it, as yet, only in the Delaware River, usually frequenting the rocky bed, but ^Iso, in fewer 

 numbers, on the mud-bottomed portions of the river. They are usually found resting under flat 

 stones, well out from the banks of the stream, where the water is of considerable depth. 

 Wherever the vegetation is dense, we have failed to find them ; nor have we seen anything to 

 indicate that it is a 'burrowing' species. .... Gambarus Bartonii, it appears to us, is the one 

 burrowing species of this locality. We have found in the deep ditches, with precipitous, muddy 

 banks, a medium-sized Cray-fish, which in most respects accords with the species called Gambarus 

 Bartonii Fabr. by Dr. Hagen. ... 



" Cray-fish are strictly omnivorous animals, but, although excellent scavengers, do not feed 

 wholly upon decayed animal and vegetable matters. We have frequently noticed that G. Bartonii 

 in an aquarium breaks ofi' the short stems of the common river weed, and eats the main stem, 

 after stripping it of its minute leaves. So the C. affinis, from beneath its sheltering flat stone, and 

 G. Bartonii, in its safe burrow, will seize the minute young cyprinoids, that pass up and down the 

 stream in such myriads, ever and aHon peeping into the various little indentations in the banks. 

 Such little fish, when once fairly caught by the big claws but by no means clumsy 'hands' of a 

 Gambarus, have no chance of escape, and are soon torn to pieces." ' 



Gambarus Bartonii described by C. Girard as G. Diogenes, constructs very interesting bur- 

 rows on the meadow flats of the Potomac River at Washington, which Mr. Girard describes as 

 follows :^ 



" The holes, as they appear at the surface of the ground, are nearly circular, from seven-tenths 

 of an inch to one inch and one inch and a half in diameter. The depth of the burrows varies 

 according to the locations ; this we generally found to be from sixteen inches to two feet, and 

 sometimes to three feet and more. The construction of tne burrow itself is often exceedingly 

 simple ; from the surface of the ground the excavation exhibits gradual slope, in direction more 

 or less undulating, for a distance of from five to ten inches, when it becomes vertical for six or 

 eight, inches, and then terminates in a sudden bottle-shape enlargement, in which the animal is 

 found. The bottom of the burrows having no subterraneous communication, no other issue except 

 towards the surface, it is entirely isolated from its neighbors, and leaves no chance of escape to its 

 inhabitant. The same burrow may have several external holes connected with it, several inclined 

 channels, which, however, meet at the depth where it becomes vertical. We constantly found the 

 cavity full of water, but this was in March and April ; the bottom, for several inches, was filled 

 with a soft and pulpy mud. 



' Proc. Phila. Acad. Nat. Sci., vi, pp. 88-90, 1854. 



