ORTMANN: monograph of the naiades of PENNSYLVANIA. 145 



Tennessee-drainage : 

 Mountain IViik Flint River, New Market, Madison Co., Alabama (H. E. Wheeler)." 



Western and southwestern localities: 

 Flat Creek, Sedalia, Pettis Co., Mis.«ouri (W. J. Utterback) (typical!). 

 Wakarusa River, LawTence, Douglas Co., Kansas (R. L. Moodie) (typical!). 

 Sabine River, Logansport, De Soto Parish, Louisiana (L. S. Frierson).""' 

 Lake Providence, East Carroll Parish, Louisiana (.Juny collection).'"' 



The Carnegie Museum possesses additional material, chiefly from southern and southwestern 

 localities, but these are local forms or races, with which I am not familiar, and so I do not discuss them 

 here. There are specimens at hand from the Alabama-drainage, in part labeled .4. hallenbecki Lea bj' 

 Walker. They are very close to A. grandis, and if they are actually hallenbecki, this name should also 

 probably become a synonym of .4. grandis. 



Distribution and Ecology in Pennsylvania (See fig. 14) : As has been mentioned 

 above, the typical A. grandis is a form characteristic of smaller creeks. It decidedly 

 avoids the larger rivers, and is not found at all in the Ohio and Allegheny, and from 

 the Monongahela only a single individual is on record. This holds good also 

 farther down the Ohio. In the tributaries, however, it is not rare, and becomes 

 most frequent in the smaller headwaters. 



In these creeks it prefers quiet pools and eddies, often below riffles, where it 

 sticks in fine sand and mud. Occasionally it is found in riffles, but then probably 

 washed out of deeper and more quiet places. Yet it is to be seen that the typical 

 form by its somewhat stronger shell is adapted to a stronger flow of water, since 

 even in the quiet pools of small streams a stronger current may prevail during 

 periods of high water. 



Under these conditions this species is found rather uniformly over western 

 Pennsylvania, alid goes eastwards to Warren, Indiana, and Westmoreland Cos. 

 But it is also capable of living in rather different surroundings, namely in ponds 

 and lakes. But we have seen that special forms develop under these conditions. 

 However, with the exception of a few glacial lakes, this environment is not often 

 found in western Pennsylvania, and there is a remarkable lack of ponds in the 

 southwestern part of the state. Thus the pond forms are rather scarce in our 

 region, as may be seen from the records given above, and we notice that they 

 often turn up in isolated ponds (Harmarville, Edgeworth, Idlepark), where there 

 is apparently no connection with streams inhabited by it. This has been observed 



«' A large, thick-shelled form, corresponding wonderfully well with Lea's original figure of gigantea 

 (Obs. II, 1838, PI. 1, fig. 1). 



'<"> A specimen absolutely indistinguishable from typical creek-forjns of Pennsylvania, possibly 

 not ciuite as thick-shelled as the average. 



"" Very much like the typical gigantea. 



