1914-] CONCEPTION AND TRINITY BAYS, NEWFOUNDLAND. 381 



scopically this rock is a very fine grained semi-crystalline limestone. 

 Calcite, frequently twinned, is the dominant mineral with quartz and 

 chlorite in secondary importance. Barite occurs as occasional small 

 and large irregular grains. Hematite is found bordering calcite 

 grains and fossil fragments or replacing them, and as irregular accu- 

 mulations. Pyrite is found occasionally. Certain nodular or pebbly 

 forms, isotropic under crossed nicols, are, because of their fineness 

 of grain, of an indeterminable nature. 



A very noticeable feature of this section is the diversity of Hyo- 

 lithes forms, some elliptical and concentric and others circular, either 

 entirely or partially replaced by calcite or hematite. The circular 

 forms measure .287 mm. in diameter (Fig. 4, Slide 250). 



Fig. 4. Microphotograph of limestone, 219 B5C; slide 250; enlarged 22 

 diam. a, hyolithes with calcite and chlorite ; b, calcite ; c, quartz. 



219 B 5d. The upper subdivision of this bed is of interest mainly 

 on account of the mineral associations in the large nodules on its 

 surface. Dififerential erosional effects between the limestone and 

 nodule have resulted in a greater conspicuousness of the more resis- 



