Flower during a series of dredgings in lower Delaware Bay collected bottom 

 material retained on a 1/4 x 3 inch mesh screen . In this material he counted 93 7 

 dead drills . Seventy -six of these had been drilled by other Uro salpinx and 

 Eupleu ra . The figures of dead drills undoubtedly represent an accumulation over 

 a long time . 



Other Species of Drilling Gastropods 



F . B. Flower (1954) in his examination of dead drills from Delaware Bay 

 reported in the preceding section, made the start! uig observation that 100 of the 

 937 dead Uro salpinx and Eupleu ra had been perforated by a species of Polimces . 

 By confining three Polmices duplicates and 23 Urosalpinx cinerea in an aquarium 

 he obtained similar destruction of Urosalpinx. by Polmices . At the end of four 

 months only one moon snail and one oyster drill were alive . The other two moon 

 snails and 22 drills had been drilled and consumed by the moon snail(s). Preda- 

 tion of oyster drills by Polimces has not been reported before. 



Cole (1942) and Orion and Lewis (1931) clearly demonstrate the progress- 

 ive replacement of the English drill Ocenebra by Urosalpinx in the River Blackwater . 

 The other English drill Nucella has also decreased markedly in recent years. Some 

 of this replacement may be attributed to the higher tolerance of Urosalpinx to 

 severe winters . How aggressively Urosalpinx has competed for food and other 

 requirements is not known. 



Sea Stars 



Mead (1900) noted that sea stars, especially when young, are exceedingly 

 voracious feeders, and prey upon a number of organisms including oyster drills. 

 He suggested that Urosalpinx may be held in check to some extent by Asterias. 

 Coe (1912) stated that_A_. forbesi is occasionally of actual benefit in that it devours 

 U. cmerea, but does this only when oysters or other bivalves are not obtainable. 

 This has been corroborated by Engle (1940, 1954), A. Flower (Clancy, pers.com.), 

 and Loosanoff (pers. com.). Engle (pers. com.) believes that when sea stars and 

 oyster drills exist together a considerable number of drills are consumed by the 

 stars. That sea stars even when present in large concentrations in company with 

 oyster drills have not eradicated the drills is shown in Long Island Sound (Glancy, 

 pers. com.; Engle, pers. com.), and Shark River, New Jersey (Carriker, unpub ) 

 Neither is it known whether Urosalpinx control the abundance of sea stars . A 

 series of observations by the writer in Gardiners Bay, New York, during the 

 summer of 1953, very strikingly demonstrated the almost total absence of sea 

 stars and a phenomenal abundance of Urosalpinx in areas where temperature of 

 the water did not rise above the tolerance limit of sea stars. It is recognized, 

 of course, that this condition may represent a chance disproportion of these species 

 without relation to possible predatory control, particularly of small sea stars by 

 drills . 



89 



