284 The American Geologist. November, 189T 
ceivecl b}'^ this coral. Palceophylhim ruyosum Billings, the 
type species, I have not investigated, but the author himself 
says : "This genus only differs from Peirai.a or Streptelasm(( by 
forming long fasciculate or aggregate masses^ instead of being 
simple," (loc cit.). Even if truly observed would that one 
character be necessarily of specific or generic im.portanee? 
I have not observed true budding in any of my specimens of 
S. profundum, much less true fission. 
Distortion due to fracture of the corallum and later mend- 
ing of it is not rarely observable in specimens from all hori- 
zons, (see fig. 3-4. pi. XVI), and if some individuals were wound- 
ed and recovered, others probably did not recover. Herein may 
be an explanation for the difference in average size between 
those from different horizons and localities since predaceous 
enemies, possibly Asaphus gigas, or again disturbances by 
water currents, and perhaps several such causes determined 
together their average size, and this in different times differ- 
ently. There were certainly some causes or conditions in their 
surroundings, affecting probably the food supply to which 
may be ascribed certain constriction and expansion rings with 
which many examples are marked. Even the relative acute- 
ness of the apical angle may be attributed to relative poverty 
of food supply. The curvature often changes in degree at some 
constrictions or by several of them. (See fig. 3, pi. XVI.) 
The wall which is without visible epitheca is marked on the 
exterior by fine transverse rings and by longitudinal furrows, 
that coincide with the position of the septa as well known. 
Nicholson says in his Manual of Palaeontology, p. 297, "A true 
theca does not seem to be present but the septa become much 
thickened towards their outer edges, being fused with one an- 
other by their lateral margins for a considerable distance, and 
thus giving rise to a dense false wall." But the original fig- 
ures accompanying it as well as the description itself are 
evidence that specimens from which the theca has been etched 
away are being described. If the figured section (op. cit. fig. 
127B) represented the external wall it would by its structure 
prove the cell margin to be vertically notched. But growth 
rings when preserved show that the margin was not vertically 
notched. The mai'gin of the cell is perhaps never preserved 
but it was evidently the outer edge of the theca and was very 
