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quent publications relating to the rocks of tliis region. The 

 present discovery, therefore, will be a matter of surprise as well 

 as gratification to those who have given attention to this obscure, 

 and hitherto unproductive, portion of our geology. 



It is true, that in view of the lithological characters of these 

 altered roclis, and their relation in strike and position to tlie car- 

 boniferous strata adjoining them towards the southwest, in the 

 contiguous parts of Massachusetts and Rhode Island, they have 

 of late been considered as probably belonging to parts of the 

 Paleozoic series, inferior to the coal measures, and including por- 

 tions of the Devonian and Silurian systems. But the want of 

 any positive evidence derived from fossils has, until now, left us 

 without a clue to the actual Paleozoic age of any part of the 

 group, and has indeed given a character almost purely conjectural 

 to speculations in regard to the epoch of the group at large. 



In respect to the zoological relations of the Braintree Trilobite, 

 Prof. Rogers remarked, that from the imperfect examination he 

 bad as yet given these fragmentary specimens, lie was dis[)Osed 

 to consider it as closely allied to the forms of Paradoxides, de- 

 scribed by Green, in his monograpli of North American Trilo- 

 bites. Of the two species described by Green, viz: P. Harlanl 

 and P. Boltoni, only the latter has been recognized by Prof. 

 Hall among our Appalachian fossils. This, under the generic 

 head of Platynotus, and more recently of Lichas, he describes as 

 a characteristic form of the Niagara group. Leaving the pre- 

 cise affinities of our fossil for future examination, there can be 

 no hesitation, from its general facies, in referring it and the in- 

 cluding strata to a date among the more ancient of the Paleozoic 

 formations. 



The rock in which these fossils occur is a ratlier fine-grained? 

 bluish-gray, siliceous slate or slaty sandstone, forming part of a 

 narrow belt of siliceous and argillaceous slates and grits ranging 

 along the northern edge of Braintree. The fossiliferous layers 

 are exposed in a quarry, vvhicli has been wrought for several 

 years past to obtain ballasting material for some of the wharves 

 in Boston, within which no doubt many of these fossils might be 

 found among the piles of stone. The fossil casts occur not only 

 on the parting surfaces of the strata, which are covered by a 

 somewhat argillaceous and ochreous coating, but also in the 



