collected in Hampton Roads, Virginia, in two regions with average summer 

 salinities of 15 and 20 o/oo possess a salinity dealn point of about 11 .7-12 .5 

 o/oo . He explains that the discrepancy between the death point salinity observed 

 in the laboratory and the salinity below which drills were not found in Hampton 

 Roads during the summer, i.e., 15 o/oo, arises from the fact that in the spring 

 salinities in these waters fall as low as 12 o/oo, figures close to the experiment- 

 ally determined salinity death point of 12 ,5 o/oo. 



In his laboratory investigations Federighi placed 20 to 50 drills in a 

 container for each salinity tested and held the drills under water by means of a 

 wire screen stretched below the surface . The water was not changed during the 10 

 day testing period The use of metal screens (kind not mentioned) for this purpose, 

 particularly if galvanized, is highly questionable since such ions are toxic to many 

 aquatic organisms when present in concentrations above low levels, and may explain 

 in part the death rate of drills in some of Federighi's higher salinities. Federighi 

 draws attention to the fact that his experiments illustrate the narrow margin of 

 salinity safety for drills living in relatively low salinities as contrasted to a 

 broader range of non lethal salinities for those in relatively high salinities , 



In similar laboratory studies in Delaware Bay, Sizer (1936) showed that 

 at summer temperatures drills survived two weeks in salinities between 15 and 

 30 o/oo; insalinities of 5, 35, and 40 o/oo all drills died in four days, and in 

 10 o/oo died a few days later Engle (1935-36) concluded that salinities above 35 

 and below 10 do not support drills, and that between 30-35 and 10-15 o/oo the 

 vitality of the drill is reduced, Laboratory experiments by Galtsoff et al. (1937) 

 indicate that a salinity of 11 o/oo kills drills and that this salinity constitutes a 

 natural barrier to the distribution of the gastropod Water fresher than this killed 

 drills more quickly: in 10 o/oo they died in 7 days; in 5 o/oo, in 4 days , 



In an evaluation of earlier work in this field, Stauber (1943) stresses the 

 important fact that the factors of time and temperature were not adequately em- 

 phasized, and suggests that instead of Federighi's term "salinity death point" the 

 more accurate term " salinity death time" be substituted He adds that although 

 Federighi computed his value as that point at which approximately 50% of the drills 

 died in the specified time intervals his data show that a few drills survived the 

 experimental, procedure . 



The fact that heavy spring rainfall repeatedly reduces salinities in Delaware 

 Bay to low concentrations and for long periods of time, which by all previous in- 

 formation on salinity death times should have destroyed drills over large areas of 

 the bay — but do not, prompted Stauber (1941; 1943) to undertake a laboratory 

 reinvestigation of this problem , H2 confined groups of 10 to 15 drills in dishes 

 containing sea v/ater of the desired salinity which he changed daily at first and less 



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