132 
BULLETIN OF THE LABORATORIES 
in oulline and separated by thin walls. These walls are most readily 
detected in weathered specimens, on account of yielding most readily 
to the dissolving action of the atmosphere. In cross sections 
they are seen as thin wavy outlines separating the vesiculose 
tissue of adjacent polyps. On account of the confused structure of 
this tissue these walls are then seen only on careful examination, but 
then they are marked enough. The interior of the polyp is filled with 
vesiculose tissue about the walls without traces of lamellae, next comes 
a zone in which the vesiculose tissue is combined with radia- 
ting lamellae, the vesicular tissue itself becomes more regular in 
arrangement and tends to combine in more or less circular rings 
around the more central portions of the polyp. Near the centre these 
rings usually become suddenly indistinct or entirely vanish. In this 
case they represent the more typical characters of the genus. In 
adjacent polyps the variation may be more gradual and then one of 
the more conspicuous characters of the genus fails. In one of the 
numerous polyps with this compound structure which may be taken as 
typical, the diameter of the entire polyp is 9 mm; the diameter as far 
as the exterior limit of the area of mixed lamellae and vesiculose tissue 
is 5 mm. The diameter of the last easily seen ring at the interior 
limit of the vesicular tissue is 2.5 mm. Longitudinal sections show 
the vertical lamellae towards the centre and the vesicular tissue quite 
strongl)^ ascending forming on the average an angle of about thirty 
degrees with the centre of the polyp although this of course is very 
variable. 
Spongophyllum Sedgivicki^ Edwards and Haim in British Fossil 
Corals, plate 56, figure 2d, is a similar form but smaller. The Austra- 
lian species is new. A description of the calyces is still necessary 
before science can be burdened wiih another name. When that is 
accomplished spongo^ylloides might not be an inappropriate term. 
C , > 11*7) 
Pleurodictyum problematicum, Goldfuss ? 
{Elate XIII, Ftg. 22.) 
Fossils found in the form of casts. Corallum compound, com- 
posed of polyps intimately united by their walls. The walls are per- 
forated, the perforations connect the cells of adjacent polyps. The 
base of the corallum is flat; there being no polyps here to connect the 
