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POPULAR SCIENCE REVIEW. 
F.G.S., of Bacup, exhibited and described a number of very fine specimens 
of fish of the genus Acrolepis, new to science, which he had obtained from 
the debris brought out in excavating a tunnel through Wadsworth Moor, 
in the neighbourhood of Hebden Bridge, near Halifax, in a bed of fine black 
shale, separating the third from the fourth, or Rinderscout Grit, the 
principal specimens having been obtained from nodular concretions which 
abound in the shale at this horizon. The specimens comprise two nearly 
perfect heads (in the jaw of one a tooth is exhibited in situ), and several 
parts of the body, illustrating the form and structure of the fish, amongst 
which are the remains of two or three fin-rays. The scales and head-plates 
are beautifully ornamented and covered with a fine enamel, the former being 
rhomboidal in form and profusely sculptured, having a number of distinct 
waving ridges and furrows traversing them in the direction of their longest 
axis, varying in number according to the position they occupied on the body 
of the fish, the ridges having a strong tendency to bifurcate, and not unfre- 
quently to further subdivide into two or three branches, these often again 
converging and becoming re-united. The genus Acrolepis has been figured 
by Professor Agassiz, MM. Coy and King, the specimens having been ob- 
tained from the magnesian limestone of this country and Germany. The 
specimens, however, under consideration have much larger scales, and differ 
in the style of ornamentation, as well as in many other essential particulars, 
from any of the figures referred to, leaving no doubt as to their constituting 
a new species of this rare fish. The discovery also carries this genus into a 
new horizon, which has previously been considered as almost barren ground. 
It is now known to be co-extensive with the carboniferous system, ranging 
from the mountain limestone through the millstone grit and coal measures 
into the Permian formation, where it appears to have attained its maximum 
development, its remains having been found there more plentifully, both 
in our own country and on the Continent, than in any of the older members 
of the system. It is intended shortly to have the specimens described and 
figured, so that the palaeontologist may have an opportunity of judging of 
the value of the discovery. In addition to the specimens above referred to, 
Mr. Aitken also exhibited remains of four or five other genera of fish, viz. 
Acanthodes sp. Cladodus, Rhizodus, Ctenocanthus and Palaconiscus, to- 
gether with a considerable variety of other fossils, all from the same 
locality. — [We may mention that these statements have been made to us 
by a correspondent who has given no name or address.] 
MECHANICS. 
An Ingenious Form of Pyrometer has been devised by Mr. Bailey. It is 
used for indicating heat, saving coal, and promoting uniformity of produc- 
tion in malt-kilns, ovens, and in other places where a certain degree of heat 
is requisite. The pyrometer for malt-kilns is 4 ft. long, and has an enamel 
dial 4 in. in diameter ; the dial is indicated to 4 300° — black figures on a 
white ground. One of these pyrometers has been tried at the Valley Mill, 
near Holyhead, and the proprietor has tested it and found it very sensitive 
