MUSEUM OF COMPARATIVE ZOOLOGY. 127 



sistent contrast between the features of the upper contact in the western 

 and eastern sheets. These need not be again stated ; suffice it to say 

 that the features of the western sheet demonstrate the trap to be sec- 

 ondary to the sandstone, while those of the eastern sheet are equally 

 conclusive in showing the sandstone to be secondary to the trap. It 

 does not seem too much to say that all the many peculiar features of 

 these two sheets find reasonable explanation as consequences of the 

 strongly different conditions of their origin. 



The localities referred to above as yielding trap frtigmeuts, but not 

 lying on the back of a trap sheet, are the trap conglomerate of the 

 anterior to Lamentation Mountain, which is certainly the stratigraphic 

 equivalent of the adjacent trap sheet ; the heavy trap conglomerates 

 northeast of the first posterior ridge to Saltonstall Mountain, which are 

 perhaps to be associated with the posterior, although probably dislo- 

 cated from it by faults ; and a single case south of Durham, where one 

 fragment of vesicular trap was found in a conglomerate, distant from 

 any trap sheet, but near the eastern crystalline boundary of the for- 

 mation. 



Meriden Quarry. Locality 19 (Figs. 5, 18). — The Meriden City 

 quariy, in the easternmost ridge of the Hanging Hills group, has been 

 attentively studied, and with much profit. Suites of specimens were 

 carefully collected from above and below the surface of separation be- 

 tween the upper and lower masses of trap which appear here, with a 

 view to examining the evidence of double flow presented. Numerous 

 specimens were also taken from the linear breccias of sandstone and 

 trap fragments which traverse the quai'ry, in order to compare them 

 with- fragments of sandstone included in trap, such as occur in a dike 

 at Mount Carmel, locality 27, several miles to the southwest, and to 

 discover if they should in any way bear on the intrusive or extrusive 

 origin of the Meriden sheet. 



The lower mass of trap, a, a. Fig. 18, is seen beneath the upper, h, 5. h, 

 on the west side of the quarry, where abundant evidence may be found 

 to show that the two were produced by separate eruptions. They are 

 divided by a somewhat irregular surface, like that of rolling ropy lava, 

 and usually marked by a seam, more or less open to the weather. The 

 lower trap is changed to a reddish brown color for a depth of three feet 

 or more below its upper surface, and contains numerous amygdular areas 

 of chlorite, giving it a mottled appearance, simulating an altered sand- 

 stone to the eye. The reddish brown color gradually disappears down- 



