and West Mersea, Essex, where American oysters have been laid down for many 

 years . The eastern American drill is very abundant in the JLiver Blackwater and 

 the Raver Colne; it occurs abundantly in the River Crouch and even more abundantly 

 in the TCiver Roach. It seems likely that Urosalpinx w as introduced into the Roach - 

 Crouch River system on Littorina or on oysters shortly before 1934 . On the Kent 

 coast Urosalpinx occurs sparingly at the mouth of the River Swale, which is apparently 

 an unfavorable habitat since it never has become abundant there in spite of numerous 

 importations of oysters from Essex. Cole points out that some habitats are more 

 favorable for the survival of Urosalpinx than others, and thus may not necessarily 

 become established in all areas where introduced. Examples of this have already 

 been given for the west coast of North America . 



Other Areas 



According to available records Urosalpinx cinerea is not found beyond the 

 geographic range already described for it in the previous sections. Further zoo- 

 geographic research and continued transportation of living shellfish by man will 

 undoubtedly extend its recorded range. 



U. cinerea is lacking m collections made in Holland (Korringa, pers. com.) 

 and in the Netherlands, Belgium, and France (Jutting, pers.com.). Korringa 

 believes that because of the shortage of oysters in England and the consequent ship- 

 ment of oysters there from Holland and France the danger of introduction of the 

 American drill into Europe is minimized. 



No American drills have ever been found in South Africa (Korringa, pers . 

 com.; Day, pers com.) even though experimental shipments of oysters from "Europe 

 are now being cultured in Knysna. Day believes Urosalpinx may be introduced on 

 these oysters, but Korringa thinks this very improbable since oysters are being 

 shipped from Arcachon or Brittany where Urosalpinx does not occur. 



Nor has mention been found of the occurrence of JJ_. cinerea in Australia 

 (Roughley, 1925) or in Japan (Cahn, 1950). Pilsbry (1895) lists the genus Urosal - 

 pinx a s occurring in Japan, but not the species U. cinerea , 



Temporal Distribution 



A few scattered reports faintly suggest that the size of drill populations 

 may fluctuate over long periods of time Ingersoll (1881) remarks that the 

 disappearance of the drill from certain restricted localities for a long time is 

 unexplained, and cites an instance in 1878 when the drill was very destructive 

 in the waters around East Point, New York, only to practically disappear after 

 that Dall (1907) states that drills once numerous on planted oyster beds in 



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