64 



THE NAUTILUS. 



timber was removed from the ship's hold. The success of the 

 zebra mussel as a colonist has been remarkable. It has spread 

 from one locality to another until it has stations in some 

 twenty English counties. In Scotland it is common in the 

 Paisley canal and in the Forth and Clyde canal, where it 

 used to be found 'in vast abundance.' Even in the most out- 

 of-the-way places it has succeeded in obtaining a hold and in 

 making headway; it is a common member of the fauna of 

 water-pipes, and in 1912 a stoppage of the water supply at 

 Hampton-on-Thames led to the discovery that the diameter 

 of the 36-inch main for unfiltered water had been reduced to 

 9 inches by masses of zebra mussels which were growing at- 

 tached to the inside of the pipe. Ninety tons of the shells 

 are said to have been removed before the main was again put 

 in working order." 



These are both interesting examples of introduced species 

 becoming pests. It is a problem that is always confronting 

 us and constant care should be taken, for we already have too 

 many similar cases. In this country, to my knowledge, the 

 oystermen have never complained of the Crepidula, nor have 

 I ever heard of its being so prolific. The possibilities of a 

 fresh- water shell like the "zebra mussel" being introduced is 

 very great. There is entirely too much reckless dumping of 

 aquaria into our ponds and streams. A number of foreign 

 fresh-water shells, etc., have been introduced in this way. 

 Why not the mussel? This was the way the water-hyacinth 

 was introduced into the St. Johns Eiver, Florida. C. W. J. 



SHELLS IN LURAT CAVERN: The loose dirt collected from 

 shelving places in the Luray Cavern, Luray, Page County, 

 Virginia, by Mr. James B. Clark on October 9, 1921, was 

 found to contain many fragments of Polygyra fraudulenta 

 Pils. and Polygyra thyroidus Say, associated with bones of 

 bats and mice. The material was gathered about 200 feet 

 down and about i/4 of a mile from the entrance of the cave. 

 All the specimens are in the collection of the Academy of 

 Natural Sciences of Philadelphia. 



E. G. VANATTA. 



