STUDIES OP THE OYSTER DRILL 
95 
The data shown in Table 5 are few because the possibility of the loss of the 
identification mark is great and the probability of recovery from depths in which the 
drill can not be seen is small. The largest loss occurred because of the inability to 
recover drills from areas not having oysters. 
The data obtained at Hampton Roads demanded a further study of the move- 
ments of the drill at Beaufort where, owing to the shallow waters, more satisfactory 
results could be obtained. The oyster beds in this region are either exposed at low 
water or are just below the low-water mark. The method employed was similar to 
that used at Norfolk, except for some few minor changes. At low water a stake was 
driven in the desired locality, and the tagged drills planted. Each day, at low water, 
the locality was visited and the movements of the drills noted. Since the tags were 
numbered, it was possible to observe the movements of each drill day by day. 
The results obtained corroborate the observations made at Hampton Roads. 
In every case, even after one month, the tagged drills had not moved over 10 to 15 
feet from the original place of planting. This was not due to the presence of unlim- 
ited food, because in one case the drills were placed on a hard bottom about 20 feet 
from an oyster bed and in no case did the drills move to it. 
Migration experiments at Hampton Roads and at Beaufort have shown that 
Urosalpinx cinerea does not migrate extensively. This is supported by other evi- 
dence. In the study of the distribution of the drill over Hampton Roads it was 
observed that contiguous oyster beds which had been left undisturbed for two years 
were infested by oyster drills in different quantities — an observation that was cor- 
roborated by several oystermen. The conclusion seems obvious: If any migration 
does take place such a condition could hardly exist, even though the presence of 
unlimited food might prevent any pronounced movements. The greater infestation 
of planted grounds over “natural rock” can not be explained except by the assumption 
that the drill does not migrate. An analysis of the older literature also supports this 
conclusion. Although this species inhabits the waters from Maine to Florida the 
greatest infestation obtains in Chesapeake Bay and in the waters north of it (Rathbun, 
1892; Collins, 1890; Hall, 1894; Rowe, 1894; Moore, 1897; Nelson, 1922, 1923; 
Rich, 1924, 1925), while south of this body of water the pest is insignificant (Ryder, 
1883; Dean, 1892; Ruge, 1898; Swift, 1898; Moore, 1898; Grave, 1905). Side by 
side with this observation is the fact that oyster culture is practiced intensely only 
in the northern waters ; in the southern waters oyster farming is rare. Does not this 
indicate that oyster planting has something to do with the distribution of the snail? 
How is the species distributed? In the author ’s opinion the agency of distribution 
is primarily the oysterman. Note his planting operations and the above conculsion 
is inevitable. The author has known a planter to move 60,000 bushels of oysters 
from a very badly infested area, having a salinity sufficiently low so that the drills 
were not doing much damage. Without screening or even forking they were trans- 
planted to another area not so heavily infested but having a more favorable salinity. 
In one year the new bed was almost a total loss. Though the greatest distributor 
is the oysterman, there are other agencies. The crabs, especially the hermit crab, 
spread the animal. The drill attaches itself to the shell, feeds on the encrusting 
gastropods, crustaceans, etc., and is in this way carried over great distances. The 
young drills may be distributed by current if they become attached to floating 
algae, debris, etc. 
