132 J. F. Whiteaves—New Species of Ptericthys. 
after that correction is made. But as nothing is known con- 
cerning the experiments not quoted, the most favorable case 
imaginable may be assumed. Suppose that in addition to the 
three results given, they were in possession of an infinite num- 
ber of others, all agreeing exactly with that which is used in 
their computation. The extreme results would still cover a 
wide range, from 9°7997 to 9°7952. Instead of the latter num- 
ber they give 9°7958, but they have made a miscalculation in 
reducing the formula, the true value being as given above. 
though making some elaborate calculations concerning 
corrections which may be rejected, they reject, apparently with- 
out calculation, the correction for the arc of vibration. The 
are through which their pendulum swung was nearly 2°, and if 
a correction for this be applied it will materially alter the last 
figure of their result. In applying the correction for buoyancy 
they seem to have corrected only for the ordinary density of 
the ball and not for its “vibrating density.” The correction 
which they apply is 0016 meters, and if this be multiplied by 
15 and the correction for are also made, their result will be 
Tokio, Japan, June 2, 1880.* 
aon 
Art. XIX.—On a new species of Ptericthys, allied to Bothriolepis 
ornata Kichwald, from the Devonian rocks of the North side of 
the Baie des Chaleurs ; by J. F. WHITEAVES. 
THE nomenclature of some of the Devonian Placoderms of 
the sub-order Ostracostei of Huxley is still in a state of great 
confusion. Thus, Ptericthys Agassiz and Bothriolepis Wich- 
wald, are both quoted by Pander as synonyms of Asierolepis 
Kichwald, while the Asterolepis of Agassiz and Hugh Miller is 
regarded by the same authority as synonymous in part with 
* Received at New Haven, Ct., June 29, 1880. 
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