PAL/EOZOIC TERRANE BENEATH CAMBRIAN. 55 



calcareous nodules, which we have remarked in the Etcheminian 

 of Smith Sound. As I learn from Dr. Crosby, the fauna found 

 in these red slates includes many of the types which I have spec- 

 ified, as characteristic of the Etcheminian fauna, and no trilo- 

 bites have with certainty been obtained from them. Whether 

 these red slates are Etcheminian or not, future investigation will 

 determine, but it may with certainty be affirmed that the con- 

 ditions of deposition closely resemble those of the Etcheminian 

 of Newfoundland. Red slates have been studied at Nahant near 

 Salem, which have yielded Hyolithidae and other fossils, and 

 are probably of the same age as the red slates near Braintree. 



The lowest Cambrian zone has not been recognized at this 

 locality by its characteristic fossils, and the space where it should 

 occur is occupied by the granitic intrusion above referred to, 

 but at North Attleborough, some distance to the westward of 

 Boston, a Cambrian fauna was found some years ago by Messrs. 

 Shaler and Foerste, and the fauna described by these authors. 

 As the trilobites all have continuous eyelobes, and the species 

 MicrodisciLS bellicinctiis is common to this locality and the Proto- 

 lenus zone in Newfoundland, it is evident that this fauna is 

 Protolenian. The group of trilobites to which the above Micro- 

 discus belongs, have a series of tubercles along the anterior mar- 

 ginal fold, which had a functional meaning. Though not 

 found at St. John, these trilobites are evidently characteristic 

 of the Protolenus fauna series ; they occur with it at Attlebor- 

 ough and Conception Bay ; but they are also a common con- 

 stituent of the Cambrian fauna at Troy, N. Y., it seems therefore 

 highly probable that the Troy fauna in part at least, belongs to 

 the Protolenus zone, but with considerable variation from the 

 typical facies. The fauna is found in its integrity only in the 

 areas over which the Etcheminian fauna is known to be spread. 



It is a disappointment to the writer that he has not been able 

 to find Olenellus (sens, strict.)^ in any of the sediments de- 

 scribed in this paper, which are spread for a thousand miles 

 along the Atlantic coast of America. This has debarred him from 



1 As represented in O. Thompsoni, Hall, O. Gilberti, Meek,? O. Iddivgsi, 

 Wale, and O. Lapzvorthi and O. retiadalus, Peach. 



