41 



which I referred at the preceding meeting of the Society, I find 

 that they belong chiefly, if not altogether, to one species, which, 

 on the authority of Agassiz, as well as my own comparison with 

 Barrande's descriptions and figures, is undoubtedly a Paradoxides. 

 Of its specific affinities I will not now speak, further than to 

 remark that the specimens agree more closely with Barrande's 

 P. sphiostcs than with any other form. 



As the genus Paradoxides is peculiar to the lowest of the 

 paleozoic I'ocks in Bohemia, Sweden, and Great Britain, marking 

 the Primordial division of Barrande, and the lingidar flags of 

 the British survey, we shall probably be called upon to place the 

 fossiliferous belt of Quincy and Braintree on or near the horizon 

 of our lowest paleozoic group, that is to say, somewhere about the 

 level of the Primal rocks, the Potsdam Sandstone and the Pro- 

 tozoic Sandstone of Owen, containing Dikelocephalus in Wis- 

 consin and Minnesota. 



Tims for the flrst time we are furnished with data for fixing 

 conclusively the paleozoic age of any portion of this tract of 

 ancient and highly altered sediments, and what is more, for defining 

 in regard to this region the very base of the paleozoic column, 

 and that too hy the same fossil inscriptions which mark it in 

 various parts of the old world. 



One of the most curious facts relating to the Trilobite of the 

 Quincy and Braintree belt, is its seeming identity with the Para- 

 doxides ffarlani, described by Green, in his monograph of North 

 American Trilobites. This description, which is quite imperfect, 

 was made out from a specimen of unknown locality procured some 

 twenty-five years ago, thi'ough Dr. Harlan, from the collection of 

 our well-known mineralogist, Mr. Francis Alger. The identity 

 is, I think, established by the comparison of a nearly complete 

 specimen of the Braintree fossil with the cast of P. Harlani 

 taken from Mr. Alger's specimen, the original never having been 

 returned. Considering the perfect agreement in lithological 

 character of the matrix as described by Green with that of the 

 Quincy fossils, and the immediate recognition of this agreement 

 in mineral features by Mr. Alger on seeing my Quincy speci- 

 mens, we can hardly doubt that the original specimen of P. 

 Harlani come either directly, or through the drift scattered in 

 the vicinity, from the same fossiliferous belt. 



