52 



F. H. McLearn — Lower Ordovician 



shows that the rocks of the St. John Group are thrown into 

 closed folds, with the black slates of the highest division, the 

 Bretonian, lying in the synclines. 



In order to define more closely the syncline of previous 

 authors, the following hypothetical structure is here suggested. 

 The Ordovician slates outcropping on the north shore, and 

 which have been shown to be upright, lie in the northern limb 

 of a syncline overturned to the south, whose axis lies beneath 

 the waters of the harbour (see fig. 1). It follows from this 

 interpretation that the slates in question are not the highest 

 beds in the section but are overlain by higher strata in the 

 center of the syncline beneath the harbour. The lower 

 Dictyonema beds do not outcrop, because on the southern limb 

 they are submerged and on the northern they are cut off by the 

 fault. 



The fauna. — Graptolites are abundant at two horizons, 

 Bed A, 8 to 10 feet above the fault, and Bed B, from 20 to 25 

 feet higher. Between them, or 18 feet below the top, is an 

 inch bed of badly crushed orthoids, more or less replaced by 

 pyrite. The graptolites are often much distorted by deforma- 

 tion, making their identification difficult and sometimes uncer- 

 tain. In the following table the collections from the two 

 graptolite horizons are kept separate : 



St. John, N. B., Siispension Bridge, Division 3d (Matthew) 



Loganograptus logani Hall . 



Tetragraptus quadribrachiatus (Hall) 



T. similis (Hall)? 



Didymograptus extensus (Hall) 



D. nitidus (Hall) 



D. patulus (Hall) 



D. hirundo Salter ? . 



D. simulans Elles and Wood 



D. v-fractus Salter 



D. acutidens Lapwortb, new var 



D. gracilis Tornquist . . . _ 



Phyllograptus ilicifolius Hall 



Protistograptus minutus (Matthew) . 

 P. corrugatus (Matthew) 



Bed A 



Bed B 



r 





r 







r 



cc 



cc 



cc 



c 



c 



c 



c 





c 





r 



c 





c 





c 



r 





r 



r 



c 



c 



Eight of the above species are recorded for the first time 

 from these beds, but Ami and Matthew (1892&) also record 

 the following : 



