poitions of Delaware Bay during entire seasons when salinities below Sizer's 

 limits prevailed* Galtsoff et al. (1937) at summer temperatures found drills in- 

 active in Delaware Bay in salinities below 15 and above 29 o/oo, and most active 

 at salinities near the upper limits of this range . Stauber discovered in his salinity 

 experiments that drills are able to attach and to crawl in almost every salinity m 

 which they survive. He concludes that in Delaware Bay at low Winter temperatures 

 they can move in salinities as low as 8 o/oo. 



Drilling and feeding 



Very little is known of the effect of salinity on the drilling rate in 

 Urosalpinx. Ha skin (1935, quoted by Galtsoff et aL , 1937, without citation) in 

 summer field studies in Cedar Creek, New Jersey, found that drills ceased drill- 

 ing approximately below a salinity of 10-12 o/oo. Above this level the rate of 

 drilling was not appreciably altered by an increase of salinity up to 25 o/oo. 

 Sizer (1936) in Delaware Bay noted no apparent correlation between the number of 

 drills captured on baited drill traps and the salinity, but all this trapping (accord- 

 ing to Stauber, pers. com.) took place within the brackets of Haskin's figures for 

 no correlation . 



Growth 



Federighi (1930a) in measurements of several hundred drills found that 

 the height of Urosalpinx in Hampton Roads, Virginia, averaged 21-25 mm., and 

 that drills in Beaufort, North Carolina, collected in salinities some 10 o/oo higher, 

 averaged 13-17 mm , These data suggested to him that drills grow to a larger size 

 in brackish than in saline water . He adds that this difference in size is probably 

 not due to a difference in salinity alone, since other unknown factors may be the 

 controlling ones . 



In a later paper (1931b) he reports that the average height of drills 

 gathered in the vicinity of Woods Hole, Massachusetts, in salinities only 

 slightly lower than those in Beaufort, was 21 mm.; that of drills in England in 

 salinities approximately 34 o/oo, 29-30 mm.; and that of drills in Maurice Rivei 

 Cove, Delaware Bay, in salinities of 21-30 o/oo, 28,8 mm. (J- R - Nelson, 1931). 

 Andrews and McHugh (pers. com.) write that drills collected in the York River near 

 Gloucester Point, Virginia, are much smaller than those taken at Hampton Bar, 

 Virginia, though salinities are not greatly different. The writer is in complete 

 agreement with Federighi's conclusion that the factors which may influence the 

 degree of size attained by drills are unknown. Fundamental studies of the effect 

 of various environmental factors on the growth rate of this gastropod are much 

 needed . 



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