226 Review of ‘ Outlines of the 
ics being limited to a few testacea. The trunks, leaves, 
and, more rarely, the pericarps of various vegetables occur 
in this formation; and all of them are very different from 
known genera and species, and apparently the growth of 
a hot, rather than a temperate, climate ; and of moist, 
rather than dry, situations. The trunks, that have been 
discovered, belong to a peculiar order of plants, “ distin- 
guished by the cortical part being entirely covered by reg- 
ar impressions resulting from the petioles of fallen leaves, 
ranging around them in spiral lines.” These remains form 
but few genera, and, at the most, not above 400 species. 
Trap rocks abound in the coal fields; and this “affords 
the first instance in descending the series, in which any of 
the great formations in England appear to be strikingly 
connected with rocks of this family.” These traps are ei- 
ther of the class of greenstones, or of the dolerite class of 
the French, which is the augite rock of Mac Culloch, in 
which augite predominates. Varieties of these rocks are 
a porphyroidal trap and toadstone. They are connected 
with the coal measures, either as overlying masses, resting 
uncenformably on the subjacent strata, or as dykes, or as 
beds, conformably interstratified and regularly alternating 
with the other strata. 
Dr. Mac Culloch found, in the Isle of Sky, that a single 
mass of trap often occupied all the three positions mention- 
ol 
ee 
