78 REPORT—1858. 
On the Yorkshire Flagstones and their Fossils. By W. Batyes. 
In illustration of the origin of this rock, the author relates the following observa- 
tions. Ona bleak moor side, in the shelving formation of a fine sandstone, was a 
hollow dammed across for the accumulation of rain-water for scouring purposes. In 
a few years it was filled up by a gradual deposit of sand. When dug out, there were 
presented finely laminated strata. In noticing other depositions, the author found 
that each layer was the deposit of one shower; and in proportion to the quantity or 
time of each succeeding rain, did the thickness of the deposit depend: each layer is 
the effect of one flood, a time intervening when the sand was all accumulated at the 
bottom, and the water had smoothed its surface by a very gentle action; so that the 
smoothed bed would not allow of the next flood’s deposit to mix. 
The laminz of the rock may be as thin as paper, or 1 inch thick for roofing-slate, 
or 2 or 3 inches thick, which is the Yorkshire flag, or an uninterrupted deposition of 
ages, when it becomes the cutting stone or ashlar, a number of square yards in one 
mass without any cleavage. ‘This Yorkshire flag then is but the pond deposit above 
noticed on a larger scale, and the deposit of some ancient estuary whose waters 
washed the finer particles of the carboniferous sandstone from the Halifax and Tod- 
morden districts ; but the deposition must have taken place, if not in deep water, cer- 
tainly in still water; for the smallest, yea, the faintest breeze of wind, caused the 
ripple-marks, as thousands of the freestone slabs show, in the strata overlying the flag 
formation, and the uppermost strata must have been formed in shallow water, and at 
times completely dry, as there are hundreds of acres which bear impressions of rain 
or hail drops having impinged upon the strata in process of formation. There are 
great quantities of the tracks and depositions of annelides, or, as they are locally 
termed, the earthworm. It is a formation extremely barren of animal remains. 
The Flora in the Yorkshire flag is not so numerous as in the ragged or crooked 
stone above and below, simply from its being a quieter deposit than the other strata. 
The most common fossil found in this formation and its kindred shale is the Calamite, 
some shales between the different strata being literally composed of its impressions. 
The next most common plant is the Stigmaria in profuse abundance, but very rarely 
the trunk or Sigillaria. It is quite evident that the tuberous appendages denote it to 
be a mud plant or roots. Some of the most magnificent and perfect specimens of the 
Lepidodendron are found in this strata. There are also Pecopteris nervosa and Neu- 
ropteris, &c.; as also a few fossil fruits, similar to T'’rigonocarpum ovatum, 
Only two seams of coal, namely, Halifax soft and hard beds, lie under this stratum, 
and above the great millstone grit base ; while thirty-three beds or bands of coal, with 
hundreds of varying strata, overlie this deposit within twenty miles eastward to Old 
Normanton, forming a series over 700 yards deep. 
On the Atlas and Axis of the Plesiosaurus. By L. BArrett, F.G.S. 
In a young specimen of Plesiosaurus presented to the Geological Museum of the 
University of Cambridge by ‘Thomas Hawkins, Esq., the atlas and axis have not 
coalesced, and are detached from the remainder of the cervical series. The axis is 
nearly entire; but the atlas has lost part of its posterior articular surface, and the 
whole of the second subvertebral wedge-bone. The interesting unanchylosed con- 
dition of the four bones composing the atlantal cup is a sufficient excuse for occupying 
a small portion of the time of the Section with a comparison of these bones with 
those described by Prof. Owen in the ‘Annals of Natural History ’ for 1847, and the 
corresponding parts of the skeleton of the new species of Plesiosaurus described by 
Prof. Huxley in the last number of the Geological Journal. 
We will first consider the structure of this specimen. The four bones composing 
the atlantal cup have been slightly displaced; and its shape is a little altered. The 
base of the neural canal is formed anteriorly partly by its centrum and partly by the 
expanded bases of the neurapophyses ; posteriorly the centrum is much larger, and 
forms the entire base of the canal. The upper thirds of the neurapophyses are 
much expanded and bent backwards; their inner angles have not coalesced, and there 
is no trace of a neural spine. The anterior surfaces of the lower part of the neur- 
apophyses are concave, and form the antero-lateral segments of the articular cup for 
