of Heliophyllum and Crepidophyllum. 45 
An external vesicular area feebly developed and often almost 
absent. Dissepiments of two orders :—those of the first order 
very strongly marked, and forming a series of strong ascend- 
ing ridges, which run inwards and upwards in an arching 
manner, forming the cross bars on the septa as seen in trans- 
verse sections, and appearing on the free edges of the septa in 
the calice as so many spines or teeth; those of the second 
order being more delicate, and running in an arched manner 
inwards and downwards, often producing a greater or less 
amount of vesicular tissue in the exterior zone. No true 
columella is present ; but those of the primary septa which 
reach the centre are often elevated to form a small eminence in 
the bottom of the cup. 
In the typical species of Heliophyllum the corallum is 
essentially simple, and is usually more or less turbinate and 
conical in form, as in H. Halli, Edw. & H.; H. canadense, 
Bill.; H. colbornense, Nich.; and LH. elegantulum, Nich. & 
Thoms. These primarily simple forms, however, very com- 
monly produce buds by simple calicular gemmation (see a 
paper by the writer, Trans. Royal Soc. Edinb. vol. xxvii. 
p. 238), or by what Lindstrém has termed “ uniserial gem- 
mation.” In these cases the polype, originally and essentially 
simple, sends up from its oral disk a single bud. The primi- 
tive calice may or may not be obliterated by the gradual 
growth and extension of the epitheca over it; and the secon- 
dary calice may or may not produce a tertiary bud in the 
same manner as that in which it was itself produced. Some- 
times the process stops with the production of one or two 
buds ; at other times it goes on by fits and starts, by periodic 
restrictions of growth and efforts at reproduction, till the 
corallum assumes the form of a series of short turbinate cups 
or inverted cones, superimposed upon one another in the same 
longitudinal axis, the younger upon the older. There are 
also not wanting instances, within the limits of the genus 
Heliophyllum, in which the old corallite throws out two, three, 
or more buds from its oral disk ; though this process is never 
carried so far as to produce large compound masses. Finally, 
in one form at present referred to Heliophyllum (viz. H. colli- 
gatum, Bill.) the corallum is truly and essentially compound, 
forming large fasciculate masses of cylindrical and closely 
approximated corallites. 
The epitheca is complete, usually thin, and marked with 
numerous delicate encircling lines, generally along with well- 
marked accretion-ridges. 
The form of the calice varies. It is rarely of any great 
depth, as compared with the proportional bulk of the coral- 
