ART. 21 ORDOVICIAISr TKILOBITES ULEICH 51 



Probably a more important fact is the recent discovery of excellent 

 specimens of a species of Salteria — which I propose to name Salteria 

 oderi after its discoverer — in a shale formation of Black River age 

 near the Massanutten Caverns in northern Virginia. This new 

 American species is a close but distinguishable ally of the Balclatchie 

 type of the genus, 8. frimueva Wyville Thomson. The vertical 

 range of this genus in both Scotland and America being very limited 

 the correlation significance of its two known species may well be more 

 definite than is that of allied species of more prolific and more per- 

 sistent genera common to Britain and North America. 



The American species of Salteria was found in an elsewhere as 

 yet unknown and geographically probably very limited formation 

 of mainly soft yellow or yellowish-gra}- calcareous shale, 300 to 400 

 feet thick, that lies directly beneath a great mass of darker Martins- 

 burg shale (Trenton and Cincinnatian) and rests apparently without 

 intervention of other deposits on a fair development of Athens shale. 

 Absence of the missing beds in this area is not extraordinary because 

 it has been known for 20 years that the Athens is the only formation 

 of the Blount group that extends so far north in Virginia. 



This new formation has already provided many new fossils besides 

 Salteria oderi. Among them I may mention 8 or 10 species of grap- 

 tolites, 1 or 2 species of Tretaspis^ 2 species of Calymene^ a species of 

 Encrinurus allied to E. punctatus^ a Tomqidstia, and a DalTnanella. 

 The brachiopod and all of the trilobites are more or less closely re- 

 lated to Balclatchie species. Moreover, the species of Calymene mark 

 the first appearance of their generic type in both North America and 

 southwestern Scotland. The graptolites are of particular interest 

 and stratigraphic significance in showing intermediate stages of de- 

 velopment between those prevailing in the Normanskill and Athens 

 and those marking Trenton stages. The only reasonable conclusion 

 to be reached from my study of this fauna is that it represents an 

 invasion of the Appalachian trough by a Middle Atlantic fauna 

 during some Black River age that, so far as known, left no deposi- 

 tional record elsewhere in North America. 



In view of these facts and logical deductions I feel impelled to give 

 the Balclatchie a higher position in the American section than I 

 formerly believed warranted. Perhaps it should go even a notch 

 higher than I have given it in the correlation chart on page 73. 



To further illustrate the difficulties of correlating Ordovician and 

 Silurian formations on opposite sides of the Atlantic is seems worth 

 while to give a brief account of the blind trails followed before I 

 knew positively that the Balclatchie is underlain by shale with Glen- 

 kiln- Athens graptolites. Naturally, I began the present inquiry with 

 a detailed study of Reed's monographs of the fossils of the Girvan 

 district. The Drummuck seemed fairly easy, but none of the three 



