ORTMANN: monograph of the naiades of PENNSYLVANIA. 



273 



hinge-teeth, which are more stumpy. The females of these two are entirely 

 different from those of E. nasuta, and have never the pecuhar expansion of the 

 lower margin. 



There is not much variability in E. nasuta. The specimens may be a little 

 longer or shorter in outline, and the color of the epidermis may be more greenish 

 or more browTiish. In this connection it should be mentioned that specimens 

 from Lake Erie frequently differ from eastern specimens by their rusty brown 



Fig. 28. 

 • Eurynia nasuta (eastern range). 



color, especially towards the beaks. This is the effect of the lake environment, 

 which is observed in other species from the lake. But this color is not always 

 present. As usual, specimens from Lake Erie often have very regular growth- 

 rests. In all other characters, the lake-form is absolutely like that of eastern 

 Pennsylvania. 



Localities in Pennsylvania represented in the Carnegie Museum: 



Lake Erie, Miles Grove, and Presque Isle Bay, also beach-pools of Presque Isle, Erie, Erie Co. 

 Delaware Eiver, Penns Manor and Yardley, Bucks Co. 

 Schuylkill Canal, Manayunk, Philadelpliia Co. 



Other localities represented in the Carnegie Museum: 



Douglas Lake, Cheboygan Co., Michigan (H. B. Baker). 



Otter Creek, Monroe Co., Michigan (C. Goodrich). 



Ottawa River, Toledo, Lucas Co., Ohio (C. Goodrich). 



Lake Erie, La Plaisance Bay, Monroe Co., Michigan (C. Goodrich); Sandusky Bay, Cedar Point, Erie 

 Co., Ohio (0. E. Jennings; C. Brookover); Port Rowan, Norfolk Co., Ontario, Canada (C. Good- 

 rich); Crystal Beach, Welland Co., Ontario, Canada (F. Behrle). 



Delaware-Raritan Canal, Princeton, Mercer Co., New Jersey. 



Delaware River, Fish House, Camden Co., New Jersey. 



