130 MR. W. L. SCLATER ON A NEW (Feb. 16, 
that are so prominent, the edge towards the columella dips down so 
that the septum has a strongly concave upper margin, as is shown in 
the figure (Plate XIII. fig. 5). 
The quinaries resemble the primaries and secondaries in shape, but 
are of course much smaller; those quinaries which are adjacent to 
the primaries and secondaries being much larger and more promi- 
nent than those adjacent to the tertiaries, and joined to the primaries 
and secondaries by an upgrowth of the wall. The tertiaries and 
quaternaries resemble one another, since they both have a straight 
upper margin, not concave as is that of the primaries, secondaries, 
and quinaries. All these details with regard to the arrangement of 
the septa will be best understood by the examination of the drawing 
(Plate XII. fig. 1), which gives a diagrammatic representation of the 
septa, tentacles, and mesenteries. 
All the septa are covered with granules arranged in lines showing 
the lines of growth. 
The measurements are as follows :—longer diameter 5 centims. ; 
shorter diameter 44 centims. ; height of the corallum from the base 
to the tip of the highest septum 2 centims.; height of the edge of 
the cup | centim. 
III. Comparison of Stephanotrochus moseleyanus with other Species 
of the Genus. 
In comparing S. moseleyanus with other species of the genus 
Stephanotrochus, which are four in number, all described by Mose- 
ley, from the deep sea, the first point that is noticed is the much 
greater development of the pali, which in all the other species are 
merely slight thickenings of the internal ends of the septa, but which 
in S. moseleyanus form a crown of stout upgrowths, supporting the 
internal edge of the oval disk. 
Again, compared with all the other species of the genus, the 
primary and secondary septa are very much stouter and more 
exsert, the line between the palus and the other end of the septum 
is very much more concave (see Plate XII. fig. 5). The septa form 
five complete cycles, and are remarkable for their regularity ; this is 
also the case in §. diadema, but not in the other species of the genus. 
There is no plain distinction of size between the primary and second- 
ary septa in S. moseleyanus as there is in S. platypus, diadema, and 
discoides ; but the primary and secondary septa are equal in size, and 
can only be distinguished by their position with regard to the long 
axis of the coral, as in S. nobilis. 
On the other hand, S. moseleyanus agrees best in general shape with 
S. diadema and platypus, and differs from S. nobilis, in which the 
corallum is deep and cup-shaped, whereas that of S. mosleyanus is 
flat and saucer-shaped. 
The differences between the five species are shown by the accom- 
panying diagrams (p. 131), which illustrate the arrangement of the 
septa in each species of the genus ; it will be seen that S. moseleyanus 
agrees best with S. platypus in this matter, from which it differs 
only in having the internal ends of the quaternaries turned in on to 
the tertiaries, “while in S. platypus all the septa are quite straight. 
