•506 A. E. Verrill — The Bermuda Islands. 



Cliff-crab (Grapsus grapsus) was found to be much less abundant 

 last spring than it was in 1898, and another species of Cliff-crab, 

 having the same habits (Plagusia depressa), which we found com- 

 mon at Castle Island, Bailey's Bay Island, etc., in 1898, could not be 

 found at all, last year, though we searched for it in the same places. 



That the unusually low temperature of the water that prevailed 

 in February and the first part of March was the principal cause 

 of the death of the fishes and corals, hardly admits of doubt. 

 Under ordinary conditions many of the tropical species, found at 

 Bermuda, are living in winter nearly at their extreme limit, as to low 

 temperatures, so that even a small falling off from the usual average, 

 for any considerable length of time, would be certain to prove fatal 

 to them. It is certain that a marked decrease below the usual winter 

 temperature took place during a part of February, amounting to 

 about 2° F. below the average for the corresponding periods in most 

 other years, as shown by the meteorological records. But the same 

 decrease in temperature has repeatedly occurred without killing the 

 fishes. 



Unfortunately, I have not been able to secure careful observations 

 on the temperature of the water, during February and March, 1901, 

 but any marked decrease in the average temperature of the water, 

 for a number of days, would be certain to affect the air in the same 

 way, though to a less extent. I am indebted to Mr. H. E. Williams, 

 Acting Chief of the United States Weather Bureau, for the follow- 

 ing statement of the temperature and rainfall prevailing at Bermuda, 

 during February, 1901 : 



"The mean temperature at Hamilton, Bermuda, for February, 1901, 

 was 59.5 F. The average temperature for February at Hamilton is 

 61.5. The rainfall for the same month was 5.56, being 1.16 inch in 

 excess of the normal. For March, 1901, the monthly mean tempera- 

 ture was 62.4 F., or 0.2 above the normal. The rainfall was 8.55 

 inches, or 2.90 inches above the normal. The month of February 

 was an exceedingly stormy one over almost the entire North Atlantic, 

 there being a succession of gales from the beginning of the month to 

 about the 26th. Many of these disturbances extended as far south- 

 ward as Bermuda. The weather for March was decidedly more 

 tranquil, although a greater amount of rain fell." 



That the mean temperature of the air was not sufficiently low, 

 during February and the first week of March, to have directly 

 caused the death of the fishes, is evident, because it has often been at 

 least two degrees lower during January and February, in other years, 

 without producing any such effects. 



