Vb \\b 
a : Publications of the Carnegie Museum, Serial No. 64. 
MEMOIRS 
OF THE 
CARNEGIE MUSEUM. 
4 : 0k 1; No. 6. 
W. J. HOLLAND, Eprror. 
MONOGRAPH OF THE NAJADES OF 
PENNSYLVANIA. 
‘ GENERAL INTRODUCTION. 
Part I. AnatomicaL INVESTIGATIONS. 
Parr Il. Tan System or tHe Noxra American Nasapes. 
se 
By A. E. ORTMANN, Pa.D. 
J syrtsBURGH. 
PuBLIsHED BY THE AUTHORITY OF THE BoARD OF TRUSTEES OF THE 
CARNEGIE INSTITUTE. 
FEBRUARY 15, 1911. 
