IV 



17, 14. After "weeds," insert: now recognized as an ancient congenor ol 

 the glass-sponges of tlie present ocean. (J. D. D. ; E. W. C. ; J. 

 H. ; R. P. W.) 



17, 15. Read Palceophycus. 



17, 14-17. "This remarli is far from true of most of them." (J. H.) 



17, 16. Read Craziana. 



17, 17. "as proved by Nathorst." "Not proved, but asserted." (L. L.) 

 "Hardly true of B at hotrep his and Asterophi/cus. (E. W. C.) 

 Some of these palseophycus are undoubtedly branched. (G. F. M. ) 



17, 28. "The best pala3ontologists." "The illustrious Saporta first of all." 

 (L. L.) 



17, 35. For Milltown, read Neilltown. 



18, I. Read clavatum. (E. W. C.) 

 18, 26. Read terminale. (E. W. C.) 

 18, 29. For gays read gaps. 



18,28. Prof. Stevenson writes: "I think that the Umbial rocks [Mauch 

 Chunk red shale, No. XI] of Fayette Co., down to the bottom of 

 the iron ores will have to go into the Pottsville conglomerate 

 [No. XII] ; this refers to Alloriteinaterniiiialis of the Big Bottom 

 ore of Dunbar." (MS. letter, Jan. 4, 1889.) 



For form atoms read formations. 



For niiiiima read inirilmus. (E. W. C.) 



Read Rominger's. 



Ainbocoelia bicorivexa, Claypole, n. sp. has been drawn but not 

 published and awaits Prof. Claypole's attention to it, with others 

 in the same condition. 



For Salina read Lower Helderberg (E. W. C.) 



For Montour read Columbia. (E. W. C.) 



Insert Ainbocoelia preeuinboiia. /See Appeiidix. 

 20, 26. Hamilton uppey^ shales. Better uppermost shales, tlie probable 

 equivalent of the Moscow shale of N. Y. ; for there is not suffi- 

 cient evidence that the Tiilly L. of N. Y. exists in Pennsylvania. 

 (E. W. C.) 

 20, 39. "This is doubtless a mistake ; and the fossil referred to is very likely 

 to be Ainboca^iiaplanoconvexa." (E. W. C.) Prof. Stevenson 

 crosses off the three bottom lines of p. 20, and top line of p. 21, 

 w^ith the note, "I have seen the specimen and know it to be the 

 Spirifer urii of E\ivope,=KS!pirifer planoconvexus of America, and 

 and very different from Ambocoelia umboncUa. 



Read Ainbocoelia. 



For underscribed read undescribed. 



For O, read OO. 



Read Shawnee. 



Read recognized. 



For "origin at "read original. 



Read Tr iai-thru s. 



There are no Amvionites in the Coal measures. The mistake was 

 made in Prof. Rogers' Geol. Penna. 1858 ; and in Reports L & H4 

 instead of quoting Rogers, the mistake was made of quoting 

 Stevenson. 

 24, 22. Read paradoxa. (E. W. C.) 

 24, 31. Read Aynplexus? 



19, 



3. 



19, 



31. 



19, 



39. 



20, 



4. 



20, 



4. 



20, 



5. 



20, 



6. 



21, 



39. 



99 



1. 



22, 



2. 



22, 



7. 



22, 



13. 



22, 



21. 



23, 



38. 



