16 Mr. F. M‘Coy on some new genera and species of — 
across it; a further difference is constantly observable between 
those groups in the vertical section, which is, that the interstitial 
vesicular plates of the inner area in Strombodes have their rows 
either nearly horizontal or inclining obliquely upwards from the 
axis towards the outer wall, while in Nemaphyllum on the con- 
trary they converge towards the axis above and incline down- 
wards and outwards below, so as to meet at a considerable angle 
those of the outer area which incline in the usual direction up- 
wards and outwards towards the walls; this peculiarity in the 
inclination of the interstitial vesicular plates of the inner area 
produces a marked difference in the stars on the weathered sur- 
face in the two genera, causing the inner area to form a large 
prominent oval or conical boss in Nemaphyllum, and a flat or 
deeply hollowed cup in Strombodes. A third difference between 
those generic groups is, that in the latter the vertical radiating 
lamellz are principally confined to the inner area, not existing 
in most of the species at all in the outer area, and do not reach 
the walls, while on the contrary all the radiating lamelle in Ne- 
maphyllum arise from the outer walls, are strongest in the outer 
area, and only half of them in general penetrate the inner area. 
In the latter corals also the whole vesicular structure is much — 
more minute and delicate in stems of the same size than in the 
others, and the cells of the inner area are larger than those of 
the outer, which is the reverse of what we find in Strombodes. 
As the young columns are produced from circular buds conti- 
nuing their development within the walls of the parent, it results — 
that the stems are inseparably united ; the walls defining the stars 
being one simple plate, the joint production of the adjacent 
polypes, cannot be divided, and consequently vertical fractures of 
the mass, instead of exposing the flat, striated external surface of 
the stems, pass invariably through the substance of the coral 
itself, exposing only sections of the interior; the external walls 
being only seen in those rare cases showing the extreme limits of 
a mass, or where in a section two masses may have coalesced. 
Some of the species resemble Clistophyllum, but are distinguished 
by the peculiar axis and by the cells of the imner area being 
larger and fewer than those of the outer. The genus is I believe 
exclusively palzeozoic. 
Nemaphyllum arachnoideum (M‘Coy). 
Sp. Char. Stars with from four to seven angles, and averaging 
from 6 to 9 lines in diameter ; axis very thin, 1 line wide: ver- 
tical section, inner vesicular area wider than the outer, of little- 
arched plates inclining slightly downwards from the axis; it 
takes about two of those plates to reach from the axis to the 
extent of this area, or two irregularly elongate unequal cells 
