1884.] 209 [Wadsworth. 



ondary calcite in the Lake Superior traps. If the surface of the 

 apparent fossil be examined, the lava flow is seen to be covered by 

 a hard reddish deposit, probably arising from the decomposition of 

 the surface of the crust. Beneath this coating appears the dark 

 reddish brown compact rock, containing green delessite and 

 white calcite. On a polished surface this portion is found to ex- 

 tend, with a gradually increasing coarseness of crystallization, 

 and greater alteration, until the rock mass proper, or matrix of the 

 fossil, is reached. A thin section taken of a portion of the mela- 

 phyr in the body of the fossil, and therefore, properly of the fossil 

 itself, has a grayish-brown groundmass inclosing crystals of feld- 

 spar, altered olivine grains, and amygdules of calcite and delessite. 

 The feldspars are much altered, but most show in polarized light 

 that they are triclinic. The olivine has black borders with orange 

 yellow interior portions. The groundmass is much altered and 

 is composed largely of fibrous material and dark granules. 



The form has a terminal point resembling a filled canal which 

 adds to the deceptive appearance. This was found, however, to 

 be a little nodule of melaphyr cemented to the rock massby the 

 water-deposited calcite. 



Among the reasons for regarding this form as a simulative lava 

 flow, and not a fossil, are the following : the macroscopical and 

 microscopical characters of the rock mass are identical with those 

 of the melaphyrs of Keweenaw Point, which have been proved to 

 be old lava flows. The matrix of the fossil, and the fossil itself, 

 are lithologically the same, while they form the same continuous 

 mass ; the fossil itself being a portion of a melaphyr, an old basaltic 

 lava, has a constitution inconsistent with its supposed organic na- 

 ture ; the form itself is too irregular in its outline for an organic 

 body ; and the apparent nib is a nodule of melaphyr, and not 

 material filling a canal. 



Professor Hall, regarding the form as a fossil, very kindly wrote 

 me a note, the following extracts from which I insert in accord- 

 ance with my promise to him and also to give evidence that the 

 form closely resembles a fossil : " The enclosed body I regard as 

 a fossil, and I know of nothing except the Huronia or siphuncles 

 of Orthoceratites with which it can be compared. See Bar- 

 rande's Sil. Syst. Bohemia, Vol. II, plates 231,232, 433-437. 1 



1 Also Foster and Whitney's Report on the Lake Superior District. 



PROCEEDINGS B. S. N. H. VOL. XXIII. U JAN..1S86. 



