GEOLOGY. 333 



were found combined -with it ; this, we believe, is the first instance in which 

 metallic lead, or any of its compounds, have been found in meteoric masses. 



PROOF OP THE PROTOZOIC AGE OF SOME OF THE ALTERED 

 ROCKS OF EASTERN MASSACHUSETTS, FROM FOSSILS RE- 

 CENTLY DISCOVERED. BY PROF. W. B. ROGERS. 



It is well known that the altered slates and gritty rocks which show them- 

 selves interruptedly throughout a good part of Eastern Massachusetts, have, 

 with the exception of the coal measures on the confines of this state and 

 Rhode Island, failed hitherto to furnish geologists any fossil evidences of a 

 paleozoic age; although, from aspect and position, they have been conjedurally 

 classed with the system of rocks belonging to this period. Indeed the meta- 

 morphic condition of these beds generally, traceable no doubt to the sienitic 

 and other igneous masses by which they are traversed or enclosed, would 

 naturally forbid the expectation of finding in them any distinguishable fossil 

 forms. 



I have lately been led to examine a quarry in the belt of silicious and 

 argillaceous slate, which lies on the boundary of Quincy and Braintree, about 

 ten miles south of Boston, and to my great surprise and delight I found it to 

 be a locality of trildbites. 



It appears that for several years past the owners of the quarry have been 

 aware of the existence of these so-called images in the rocks which, from time 

 to time, they have quarried as a ballasting material for wharves, but until wow 

 the locality has remained entirely unknown to science. 



The fossils are in the form of casts, some of them of great size and lying at 

 various levels in the strata. So far as I have yet explored the quarry they 

 belong chiefly, if not altogether, to one species, which, on the authority of 

 Prof. 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 farther than to remark that the specimens agree more closely with 

 Barrande's Par. spinosus than with any other form. 



The rock in which these fossils occur is a compact, dense, rather fine- 

 grained, bluish grey or olive silico-argillaceous slate or slaty sandstone, con- 

 taining little or no carbonate of lime. The fossiliferous belt is actually 

 included in a part of its course between great masses of igneous rock, and it 

 is not a little surprising that, under conditions so favorable for metamorphic 

 action, the fossil impressions should have been so well preserved. 



In regard to the distribution of the genus Paradoxides, Barrande, in his great 

 work, the Systeme Silurien de la Boheme, has the following important observ- 

 ations : 



"In Bohemia the genus Paradoxides characterizes exclusively the pri- 

 mordial fauna, and does not extend beyond our protozoic schist. The 

 twelve species which have been determined divide themselves almost equally 

 between the two slaty belts of Ginetz and Skrey, and two are common to them 

 both. In these we find the Paradoxides spinosus in all the localities which 

 have afforded fossils, while each of the other species is restricted to a few 

 points, principally those of Ginetz and Skrey. 



