3] 4 ORTMANN— THE ALLEGHENIAN DIVIDE. [April 18, 



All the others go up beyond tidewaters, and are found in the 

 Delaware River or its tributaries on the Piedmont Plateau. The 

 Allegheny Valley and its eastern boundary being obscured in this 

 region, it practically is connected with the Piedmont Plateau. The 

 Delaware River proper extends soon into the Glacial area, but there 

 are tributaries outside of it west (northwest) of the Blue Mountain 

 (Kittatinny Mountain), belonging to Lehigh River. The Lehigh 

 itself is polluted ; but I have collected in this region the following 

 species {Princess Cr. and Meniolagomeka Cr., at Kunkletown and 

 Smith Gap, Monroe Co. ; Mahoning Cr. } Leheighton, Carbon Co. ; 

 and Lizard Cr., Mantz, Schuylkill Co.). 



1. Elliptic) complanatus (Dillw.) 



2. Anodonta Cataracta Say 



3. Alasmidonta heterodon (Lea) 



4. Alasmidonta undulata (Say) 



5. Alasmidonta varicosa (Lam.) 



6. Strophitus edentulns (Say) 



Possibly the list is not quite complete (Symphynota tappaniana 

 might be here). But I never found all of these species associated 

 at a single locality, and it should be stated right here that it is a 

 general rule that on the Atlantic side certain species are of rather 

 erratic distribution, being sometimes missing at certain localities for 

 no apparent reasons, while at others they may be abundant. 



With the exception of Margaritana mar gariti fera, probably all 

 of the Delaware River species (14) were once found in the lower 

 part of Schuylkill River. Although the fauna of this river has been 

 studied for nearly one hundred years, reliable information about the 

 details of the distribution of the shells are not at hand. At the 

 present time this river is so polluted that the fauna is extinct, only 

 in the Schuylkill canal is a rather rich remnant of at least 8 species 

 (nos. 2, 4, 5, 7, 8, 11, 12, 13 of list no. 17). Thus we cannot form 

 an idea of how far the species advanced upstream and shall never 

 know this. 



In the headwaters of the Little Schuylkill River, in Schuylkill 

 Co., northwest of Blue Mountain, a very peculiar species turns up, 



