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ANNALS NEW YORK ACADEMY OF SCIENCES 
septatum and HeliophyUum corniculum, so called, do not appear to belong 
to this genetic series. The former species has been carefully studied, but 
in its early stages it seems to have no septa. The genetic relationship of this 
from is uncertain. The latter species, H. corniculum, apparently is not a 
HeliophyUum, but, as suggested by Grabau, belongs to an entirely different 
genetic series, namely Heliophrentis derived from the so called [Zaphrentis] 
racinensis of the Siluric. 
Microcyclus discus Meek & Worthen. 
This is a small flat circular coral form the Devonic beds. Duerden has 
found that in the earliest stages observable by grinding off the tip, six septa 
were present. 1 Others are added in the regular manner. In the adult 
condition the septa are more or less radially arranged and the septal fossula is 
well marked. This form seems to represent the beginning of that specialized 
line of development which ends with the retrogressive genus Hadrophyllum. 
Hadrophyllum orbignyi Edivards & Haime. 
Hadrophyllum is a genus of small size and depressed shape, having 
no hollow cup or calyx, but with the septa projecting above the exterior wall. 
Edwards and Haime, in their volume on British fossil corals, describe the 
genus thus: “Corallum short. Calice superficial. One very large septal 
fossula, and three small ones representing a cross. ^ The radiate arrange¬ 
ment of the septa somewhat irregular.” In Zittel’s Text Book of Paleotol- 
ogy this description is slightly modified and reads thus: “Cushion-shaped, 
with epitheca. Calice with three septal fossulse, that of the cardinal septum 
being the largest.” The latter description seems to be correct in regard to 
the number of fossulae or depressions adjacent to the primary septa, although 
only one of these depressions can correctly be called a fossula, the other two 
being pseudofossulae. In all the specimens examined, there is a fossula pres¬ 
ent surrounding the cardinal septum, and two lateral depressions between 
the alar septa and the septa of the counter quadrants. 
The genus Hadrophyllum is apparently highly specialized and probably 
represents the terminal member of a non-progressive or perhaps retrogressive 
series, in which the primitive pinnate arrangement of the septa, as found in 
Streptelasma profundum, has been retained and accentuated in the adult 
stage. 
The type under consideration is the type of this species, and when the 
1 Annals and Magazine of Natural History. Sept., 1906. 
