BIGELOW. — SHOAL-WATER DEPOSITS OP THE BERMUDA BANKS. 587 



of about forty degrees. But on the eastern side the slope to a depth of 

 seven hundred fathoms is more gradual, being about twenty-five degrees. 

 The bank has thus the character of a very steep, isolated peak, some six 

 thousand feet hiL;h. Although the sounding of five hundred and thirty 

 fathoms shows that there is a ridge connecting the Challenger and Argus 

 banks, on each side of which the water is much deeper, this in no w-ay 

 interferes with the isolated character of the bank as far as its fauna and 

 bottom deposits are concerned. 



Dredging on this bank was carried on from an ocean-going tug from 

 July 31 to August 2, 1903, hauls being made at a number of stations.* 

 Bottom samjjles were obtained from depths between thirty and fifty 

 fathoms. 



The only dredging ever done before on this bank was carried on by the 

 Challenger, in April, 1873, when a single haul was made while the ship 

 was anchored to allow soundings to be taken. Speaking of the results of 

 this haul. Sir Wyville Thomson ('77, I, p. 360), says, "The bank, which 

 seems to be about five miles across, consists mainly of rounded pebbles, of 

 the substance of the Bermudas ' Serpuline reef.' There is an abundant 

 growth all over the pebbles of the pretty little branching corals Madracis 

 asperula and M. hillana." Murray and Renard ('91, p. 50-51), in their 

 report on the deep-sea deposits collected by the Challenger, say that the 

 bank is covered with corals, Serpula, and calcareous pebbles. Since that 

 time the area of the bank has been developed by careful soundings, and 

 the bottom is given on the admiralty charts as coral sand ; but, so far as 

 I am aware, no other dredging has ever been done on the bank. 



Our dredge hauls brought up the same organisms as those taken by 

 the Challenger; that is, Madracis, gorgonians, starfishes, mollusks, etc., 

 together with large numbers of the calcareous pebbles, with which the 

 dredge was ordinarily filled to the mouth. These pebbles ranged from 

 two to six inches in diameter, the latter being the largest that could pass 

 through the mouth of the dredge ; but of course much larger ones may 

 occur. Neither sand nor mud was brought up by us ; in fact, no de- 

 posits whatever except these calcareous masses. These are roughly 

 spherical and of a dark red or brownish color, being entirely incrusted 

 with the nuUipore Lithothamnion ungeri, and with Serpula tubes, small 

 corals, bryozoans, and other organisms. Every one of these masses, 

 although entirely coated with organisms, showed on one side or region nul- 



* For this opportunity the Biological Station was indebted to Captain William 

 E. Myer of St. George's, who generously gave tlie use of his tug " Gladisfen " and 

 her crew for this purpose. 



