1909.] FRESH-WATER FAUNA IN PENNSYLVANIA. 93 



polluted waters; this, however, at least in certain species, is appar- 

 ently due also to direct extermination by man. The soft shell 

 turtle {Aspidonectcs spinifcr) is a good example ; it used to be 

 present almost everywhere, but it has been exterminated practically 

 in the Ohio, the lower Allegheny, the Monongahela and Youghio- 

 gheny. It is still present, for instance, in the clear waters of the 

 upper Youghiogheny, the upper Allegheny, in Lake Erie, etc. 



Among the amphibians, frogs and toads do not prefer the 

 streams ; they rather are pond and lake forms, and, besides, inhabit 

 the water only at certain seasons. They do not seem to be very 

 susceptible to the quality of the water, since they are air-breathing 

 animals, and, consequently, are still abundant, although certain spe- 

 cies show a tendency to become rare. Thus the bullfrog is met 

 with in numbers only in the northwest of the state, where clear 

 streams, ponds and lakes prevail. Yet in this case, extermination 

 by man has surely played a part. 



Of the Urodela, the smaller salamanders and newts do not in- 

 habit in large numbers the rivers and creeks, but prefer rather the 

 mountain streams, the ponds and lakes, where generally the condi- 

 tions are yet good. Thus there does not seem to be an appreciable 

 reduction of their number. The two large salamanders, the hell- 

 bender (Cryptobranchus allegheniensis) and mud puppy (Necturiis 

 maculosus) surely are influenced by the pollution, yet not directly, 

 but by the destruction of their food. They seem to be the last mem- 

 bers of the fresh-water fauna which disappear, and are occasionally 

 found where there is no other permanent life. (Hellbenders were 

 frequent in the Conemaugh River at New Florence, Westmoreland 

 Co. Nothing but a few fish and crawfish were at this locality, which 

 apparently came from a clear tributary.) 



The most important forms of invertebrates, which I have studied 

 more closely, are the crustaceans and the mollusks. Occasionally I 

 have collected fresh-water sponges, worms, bryozoans, but of all 

 these we may say that they disappear very soon after the stream 

 has become polluted. They are found only in such waters which 

 contain an abundance of other life. 



The crustaceans of the genus Camborus (crawfishes) are rather 

 susceptible, and we may say that generally the pollution of a stream 



