SCIENTIFIC SUMMARY. 
435 
GEOLOGY AND PALAEONTOLOGY. 
Discovery of the Opercula of Hyolithes. — Mr. W. S. Ford announces this- 
discovery from New York, in “ Silliman’s American Journal.” He says 
that several weeks ago, "being in Montreal, he showed Mr. Billings, Palaeon- 
tologist of the Geological Survey of Canada, a small collection of fossils that 
he had made in the Primordial rocks near New York. He pointed out to 
him, that among them there were the opercula of two species of Hyolithes. 
One is a minute circular species with four pairs of lateral muscular impressions, 
and two smaller, dorsal, all radiating from a point near one side. The other 
species is larger and like a Discina on the outside. Mr. B. showed him 
several specimens of the smaller species, that had been collected by Mr. T. 
C. Weston of the Canadian Survey last summer, in rocks of the same age- 
below Quebec. He is informed that this is the first discovery of the opercula 
of Hyolithes yet made on this continent. He has made some observations 
on the rocks of this vicinity, and collected a number of species of fossils, of 
which he hopes to give an account at an early date. 
The Geology of the Rocky Mountains . — We learn from one of our American 
contemporaries published in August, that Professor Marsh of Yale College, 
with twelve other gentlemen, has started for the Pocky Mountains and 
Pacific Coast. He will be absent until winter, and will continue his 
investigations of the Tertiary and Cretaceous formations which his explora- 
tions last year proved to be very productive in new species of vertebrates. 
What is Coal ? — This question is answered in a very able paper by Pro- 
fessor Dawson, LL.D., in the “ Monthly Microscopical Journal ” for August. 
He says that — 1. The mineral charcoal or u mother coal ” is obviously woody 
tissue and fibres of bark j the structure of the varieties of which and the 
plants to which it probably belongs, he has discussed in another paper. 2„ 
The coarser layers of coal show under the microscope a confused mass of 
fragments of vegetable matter belonging to various descriptions of plants, 
and including, but not usually largely, sporangites. 3. The more brilliant 
layers of the coal are seen, when separated by thin laminae of clay, to have 
on their surfaces the markings of Sigillariae and other trees, of which they 
evidently represent flattened specimens, or rather the bark of such specimens. 
Under the microscope, when their structures are preserved, these layers show 
cortical tissues more abundantly than any others. 4. Some thin layers of 
coal consist mainly of flattened layers of leaves of Cordaites or Rychnophyllum. 
5. The Stigmaria underclays and the stumps of Sigillaria in the coal roofs 
equally testify to the accumulation of coal by the growth of successive 
forests, more especially of Sigillariae. There is, on the other hand, no 
necessary connection of sporangite beds with Stigmarian soils. Such beds 
are more likely to be accumulated in water, and consequently to constitute 
bituminous shales and cannels. 6. Lepidodendron and its allies, to which 
the spore-cases in question appear to belong, are evidently much less im- 
portant to coal accumulation than Sigillaria, which cannot be affirmed to 
have produced spore-cases similar to those in question, even though the 
observation of Goldenberg as to their fruit can be relied on ; the accuracy of 
which, however, he is inclined to doubt. 
