June 5, 1884] 



NATURE 



127 



is rising from winter to summer than when it is falling 

 from summer to winter, agreeing in this respect with what 

 has been observed in similar regions. 



The Monthly Kecords give, in addition to the month's 

 results, the averages of that month for each station based 

 on previous years' observations. In the review referred 

 to above we drew attention to the temperature observa- 

 tions at Portland as being evidently too high. In the 

 following February (1877) the mistake was rectified, and 

 since then the observations of temperature at this station 

 agree with those made at the other stations. A comparison 

 shows that down to January 1S77 the published tempera- 

 tures at Portland were about 5°'o too high. As regards 

 the averages published since then, however, no allowance 

 has been made down to December 18S3 for this large 

 error. The result is that while at the other stations of 

 the colony the mean temperatures of the months since 

 February 1877 rise above and fall below their averages as 

 at other places, Portland all but uninterruptedly appears 

 as very much below its average. Indeed, except the un- 

 usually warm months of September 1879 and February 

 18S0, not one of the other forty-six months shows a tem- 

 perature as high as the average. It is the more necessary 

 to draw attention to this point seeing that the faulty mean 

 temperatures of Portland still continue to appear in works 

 on climatology, either in the text, or they have been used 

 along with the means of other places, similarly faulty, in 

 drawing the isothermals of the globe. 



HABITS OF BURROWING CRAYFISHES IN 

 THE UNITED STATES 



/~\N May 13, 18S3, I chanced to enter a meadow a 

 ^-' few miles above Washington, on the Virginia side 

 of the Potomac, at the head of a small stream empty- 

 ing into the river. It was between two hills, at an 

 elevation of 100 feet above the Potomac, and about a 

 mile from the river. Here I saw many clayey mounds 

 covering burrows scattered over the ground irregularly 

 both upon the banks of the stream and in the adjacent 

 meadow, even as far as ten yards from the bed of the 

 brook. .My curiosity was aroused, and I explored several 

 of the holes, finding in each a good-sized crayfish, which 

 Prof. Walter Faxon identified as Cambarus a 

 Girard (C. obesus, Hagen), otherwise known as the 

 burrowing crayfish. I afterwards visited the locality 

 several times, collecting specimens of the mounds and 

 crayfishes, which are now in the United States National 

 Museum, and making observations. 



At that time of the year the stream was receding, and 

 the meadow was beginning to dry. At a period not over 

 a month previous, the meadows, at least as far from the 

 stream as the burrows were found, had been covered with 

 water. Those burrows near the stream were less than 

 six inches deep, and there was a gradual increa-e in depth 

 as the distance from the -tream became greater. More- 

 over, the holes farthest from the stream were in nearly 

 |! every case covered by a mound, while those nearer had 

 , either a very small chimney or none at all ; and subse- 

 quent visits proved that at that time of year the mounds 

 \ were just being constructed, for each time I revisited the 

 place the mounds were more numerous. 

 The length, width, general direction of the burrows, 

 j and number of the openings were extremely variable, and 

 j the same is true of the mounds. Fig. 1 illustrates a typi- 

 | cal burrow shown in section. Here the main burro v is 

 . very nearly perpendicular, there being but one oblique 

 opening having a very small mound, and the main mound 

 is somewhat wider than long. Occasionally the burrows 

 are very tortuous, and there are often two or three extra 

 openings, each sometimes covered by a mound. There 

 is every conceivable shape and size in the chimneys, 



ranging from a mere ridge of mud, evidently the first 

 foundation, to those with a breadth one-half the height. 

 The typical mound is one which covers the perpendicular 

 burrow in Fig. 1, its dimensions being six inches broad 

 and four high. Two other forms are shown in Fig. 2. 

 The burrows near the stream were seldem more than six 

 inches deep, being nearly perpendicular, with an enlarge- 

 ment at the base, and always with at least one oblique 

 opening. The mounds were usually of yellow clay, 

 although in one place the ground was of fine gravel, and 

 there the chimneys were of the same character. They 

 were always circularly pyramidal in shape, the hole inside 

 being very smooth, but the outside was formed of irregular 

 nodules of clay hardened in the sun and lying just as they 

 fell when dropped from the top of the mound. A small 

 quantity of grass and leaves was mixed through the 

 mound, but this was apparently accidental. The size of 

 the burrows varied from half an inch to two inches in 

 diameter, being smooth for the entire distance, and nearly 

 uniform in width. Where the burrow was far distant 

 from the stream, the upper part was hard and dry. In 

 the deeper holes I invariably found several enlargements 



Fig. I Section of Crayfish bu 



Fig. 2 Crayfish mound 



at various points in the burrow. Some burrows were 

 three feet deep, indeed they all go down to water, and, as 

 the water in the ground lowers, the burrow is undoubtedly 

 projected deeper. The diagonal openings never at that 

 season of the year have perfect chimneys, and seldom 

 more than a mere rim. In no case did I find any con- 

 nection between two different burrows. In digging after 

 the inhabitants I was seldom able to secure a specimen 

 from the deeper burrows, for I found that the animal 

 always retreated to the extreme end, and when it could 

 go no farther would use its claws in defence, lioth males 

 and females have burrows, but they were never found 

 together, each burrow having but a single individual. 

 There is seldom more than a pint of water in each hole, 

 and this is muddy and hardly suitable to sustain life. 



The neighbouring brooks and springs were inhabited 

 by another species of crayfish, Cambarus bartouii, 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 



