DESCRIPTION OF CHALK CORALS. 285 
lished descriptions no allusion is made to the nature or functions of the minor 
pores, nor to the effects which age bad or might have produced on the exterior. 
From a careful consideration of the peculiarities of the coral under examination, 
and a comparison of them with the structures of other accessible or figured 
zoophytes, it is conceived that Herr Roemer was fully justified in forming the 
opinion before-mentioned ; and as neither that authority nor any other, so far as 
is known, has proposed a distinctive appellation, the term Petalopora (réraXov, 
lamina) is suggested in allusion to the vertical plates which constitute a leading 
component, not only as respects the primary, but the secondary characters also. 
Petalopora, n. g. 
Tubular, free except at the base ; framework composed of vertical lamin with 
an intermediate, foraminated structure; apertures to the visceral or tubular 
cavities distributed over the whole surface ; exterior altered according to age. 
Petalopora pulchella. (Tab. XVIII. A. figs. 7 & 7 ato 7h.) 
Czespitose, dichotomously branched, branches slender, round; surface in a 
young state, composed of a general reticulation in which occur fine vertical 
lamine, and the apertures to the visceral cavities—in a mature state traversed 
by bold longitudinal ribs, having between them the oral aperture, alsc subordi- 
nate medial ribs and rows of minute foramina—in an aged condition, apertures 
concealed, and surface wholly formed of a fine reticulation; openings to the 
visceral cavities large, circular, more or less projecting according to age, in 
general arranged quincuncially ; surface irregularities numerous. 
Chrysaora pulchella, Roemer, Verst. Norddeuts. Kreidegebirges, p. 24. tab. 5. 
fig.29. Upper chalk-marl. 
Mr. Dixon’s cabinet contains a mass of chalk about 14 inches in length and 
nearly 5 in its greatest breadth, having its whole surface covered with prostrated 
branches of Pet. pulchella, and judging by the sides of this magnificent specimen, 
the thickness of the zoophyte-stratum exceeded an inch ; but as no part of the base 
was detected, and the matrix was indented by the obtuse extremities of branches, 
the actual upward extension of the coral must have been much greater. 
The mode of branching was evidently dichotomous (fig. 7), no lateral shoots 
having been observed; and the subdivisions very generally, but not invariably, 
succeeded each other in the same plane. The angle of divergence varied from 
2P 
