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THE DEVONIAN FOSSILS OF CANADA WEST. 263 
to the diameter of one inch and a half at a length of two inches and 
ahalf. Cup about three-fourths of an inch in depth, the form of 
the bottom variable, either with a smooth space or a small pit in the 
centre, or covered with the prolonged radiating septa; these latter 
about one hundred and fifty in number; the interseptal spaces filled 
for a short distance from the outer surface with small sub-lenticular 
cells, of which there are about four in one line; a small space be- 
neath the bottom of the cup in full-grown specimens, with flexuous 
transverse diaphragms. Surface, when perfect, with sometimes a 
few inconspicuous encircling annulations of growth, but often with 
a somewhat smooth aspect, longitudinally marked with the septal 
strie, of which there are, on an average, five or six in the width of 
two lines; when partially decorticated, the interseptal spaces 
roughened with small subimbricating projections or notches, with 
their sharper edges usually turned upwards—about four of these in 
one line. The largest specimen that I have seen is three inches and 
one-fourth in length, measured along the surface of the side with 
the larger or convex curve, and one inch and a half on the lesser 
curve. The diameter of the cup, in the same specimen, is one inch 
and a half. Several others that I have seen are from one to two 
inches and a half in length. 
The arrangement of the septa in the bottom of the cup appears 
to vary a good deal in different individuals. In one specimen two 
inches in length, there is a deep septal fossette on one side, and a 
pit in the centre of the cup. The septa branch off, as it were, on 
each side of a depressed line, extending from the central pit to the 
fossette. In another, about the same size, the septa all reach the 
centre in the bottom of the cup, and are there somewhat twisted to- 
gether. There is a septal fossette in this specimen also. In a 
third individual, with a cup one inch in diameter, there is a smooth 
space two lines wide in the centre, with an obscurely indicated 
septal fossette. I think it probable that most of the large indivi- 
duals will be found to have the bottom smooth. 
The form of the walls of the cup also varies according to the 
age of the individual. In the immature it is thin, and the septa 
alternate somewhat in size. But in the large ones (three inches in 
length) the interseptal spaces are filled with the cellular tissue 
nearly to the free edges of the septa, and the wall of the cup is 
thus rendered solid for the thickness of two lines, or a little more, 
