Sortas—On Pucksia Mac Henryi. 301 
tranverse, then the original form of the threads may have been 
cylindrical. It is remarkable in this connection that transverse 
sections of the slate rarely present any other than truly transverse 
sections of the threads. In no single instance, though many 
slices were cut, has a thread been observed running directly 
transverse to the cleavage, a fact which rather tends to diminish 
the probability that the oval forms, seen in tangential sections of 
the slate, are truly transverse sections of the threads. | 
The longitudinal sections (figs. 4, 5, 6) present a median band 
of granular quartz, bounded on each side by a 
band of fibrous quartz, and though the boundary 
between the lateral and median regions is well 
defined, it is often possible to trace several marginal 
fibres into a common origin in one of the central 
Fic. 4. Fie. 5. 
Longitudinal section (x 6). The Longitudinal section (X 60). 
black spots represent iron pyrites. 
granules (fig. 5). The outer boundary is sharply marked—fairly 
even or faintly crenate, swelling out into rounded protuberances 
