PETALOPOEA. 
379' 
Figures. 
PI. XII. Fig’. 8. Longitudinal section along the lower portion 
of an old branch, X 10 clia. Chalk : Dover. Bowerhank Coll. 
D. 7062. 
PI. XII. Fig. 9«, base of a branch, nat. size. Fig. 9J, part of the 
same, X 18dia. Middle Chalk : Chatham. Gamble Coll. D. 4514.. 
PI. XII. Fig. 10. Part of a branch of var. apjoendiculaia^ 
X 10 dia. Middle Chalk: Chatham. Tine Coll. D. 713. 
Fig. 46, p. 373. A longitudinal section across a few zooecia, after 
Pocta. 
Fig. 47. The distal end of a branch, of which part has 
longitudinal ribs and serial maculae, and part has an epitheca 
which covers the ribs and has irregularly scattered maculae ; 
X 20 dia. Middle Chalk : Chatham. Vine Coll. D. 2743. 
Fig. 48. Part of a branch with a lateral gonoeeium, X 10 dia. 
Middle Chalk : Chatham. Yinc Coll. D. 2740. 
AEEI^UTIES. 
This species usually has the maculae in two rows along the front 
of each zooecium ; but a variety occurs with more than two rows, 
the polypora of d’Orbigny. Pergens remarks that that form is 
probably founded on a badly preserved specimen of P. costata ; 
and it is interesting to notice that on the label attached to the 
polyporous specimen figured by Lonsdale (Geol. Suss. pi. xviii.A, 
fig. 7(?) he has written “surface altered by age.” On that 
specimen there are some zooecia with the normal two rows of 
Fig. 47. 
Fig. 48. 
Fctalopora costata (Orb.). 
