262 Dr. R. H. Traquair—Devonian Fishes of Canada. 
remains unmelted together with the deposit are equal to the original 
thickness of the crust, then 
« ytkh'=k. 
or k’=k—y. 
Substituting this for &’ in the expression for the expansion we 
obtain 
Expansion = E (yt zl =) 
Under the now supposed circumstances we have seen that 
y=10:9 d. If then we take the crust to have been originally 20 
miles thick, this gives 
(10:9 d)? 
Expansion = E (10-9 d x 2000— 1000). 
Hence if the sea was a mile deep at first, 
Expansion = 0:0000215 x 18860 feet, 
= 1800 feet. ' 
It can be shown by substituting for y and &’ in (3), and differ- 
entiating with respect to x, which measures the melting off, that the 
greatest expansion will take place when 
c= 4 (SE + 1) 
This is a greater amount of melting than is probable. 
VI.—Notrs on THE Deventan Fisues or CAMPBELLTOWN AND 
Scaumenac Bay 1n Canava,—No. 3. 
By R. H. Traquair, M.D., F.R.S., F.G.S. 
FisHes From THE Upper Drvontan OF DaLHOUSIE, SCAUMENAC Bay. 
CrENODONTID&. 
Scaumenacia curta (Whiteaves). 
Phaneropleuron curtum, Whiteaves, Canad. Nat. n.s. vol. x. p. 21, also in Trans. 
Roy. Soc. Canada, vol. iv. sect. iv. p. 108, fig. 2, and vol. vi. sect. iv. p. 91, 
pl. v. fig. 8. A. S. Woodward, Cat. Foss. Fishes Brit. Mus. pt. ii. p. 248. 
h R. WHITEAVES in his description of this species mentions 
that “in one specimen there are indications of what looks like 
a short break or separation between the anterior and posterior por- 
tions of the dorsal (or between the two dorsals if there were two, 
which is scarcely probable), but this break may be owing to an 
accidental and abnormal fracture of the fin rays at this point, for in 
other specimens the two portions appear to be continuous.” This 
break is, however, represented in all his figures, including the 
restored sketch given in his second paper in the Transactions of the 
Royal Society of Canada. 
But on looking carefully through the whole of the extensive 
series of this species collected by Mr. Jex last summer and also on 
rat ome. 
Phew ee ee ee ee a ee 
ny hie. ene 
ee ee 
—— 
