The neighboring brooks and springs were inhabited by another species of crayfish, _Cambaras bartonii_, but although especial search was made for the burrowing species, in no case was a single specimen found outside of the burrows. _C. bartonii_ was taken both in the swiftly running portions of the stream and in the shallow side pools, as well as in the springs at the head of small rivers. It would swim about in all directions, and was often found under stones and in little holes and crevices, none of which appeared to have been made for the purpose of retreat, but were accidental. The crayfishes would leave these little retreats whenever disturbed, and swim away down stream out of sight. They were often found some distance from the main stream under rocks that had been covered by the brook at a higher watermark; but although there was very little water under the rocks, and the stream had not covered them for at least two weeks, they showed no tendency to burrow. Nor have I ever found any burrows formed by the river species _Cumbarus affinis._ although I have searched over miles of marsh land on the Potomac for this purpose. [Illustration: Fig. 2 Crayfish Mound (shorter)] The brook near where my observations were made was fast decreasing in volume, and would probably continue to do so until in July its bed would be nearly dry. During the wet seasons the meadow is itself covered. Even in the banks of the stream, then under water, there were holes, but they all extended obliquely without exception, there being no perpendicular burrows and no mounds. The holes extended in about six inches, and there was never a perpendicular branch, nor even an enlargement at the end. I always found the inhabitant near the mouth, and by quickly cutting off the rear part of the hole could force him out, but unless forcibly driven out it would never leave the hole, not even when a stick was thrust in behind it. It was undoubtedly this species that Dr. Godman mentioned in his "Rambles of a Naturalist," and which Dr. Abbott _(Am. Nal.,_ 1873, p. 81) refers to _C. bartonii_. Although I have no proof that this is so, I am inclined to believe that the burrowing crayfishes retire to the stream in winter and remain there until early spring, when they construct their burrows for the purpose of rearing their young and escaping the summer droughts. My reason for saying this is that I found one burrow which on my first visit was but six inches deep, and later had been projected to a depth at least twice as great, and the inhabitant was an old female.