DESCRIPTION OF CHALK CORALS. 305 
showed likewise a marked difference between an early arrangement and of a 
more advanced state of production. In the former condition, and along the 
middle of the branches (fig. 3 a), the equivalent representative, the large apertures 
were disposed longitudinally though not lineally, conforming to the lengthwise 
growth of the coral ; whereas on each side of this band they were for the greater 
part distributed in transverse rows (fig. 36), the component tubes issuing 
laterally, and apparently from near the back of the branch; and this mode of 
production will account for the disproportionate augmentation of breadth. Be- 
sides, were all the minor tubes in the front of a branch successively converted 
into greater, their abundance at the base of the coral would indicate a long-con- 
tinued growth of previously matured cavities in the oldest portion ; a property 
which, it is believed, does not exist among Bryozoa, even in the genus Tubulipora. 
The lateral shoots were considered as affording also evidence of the abdominal 
tubes having been original, or distinct structures. They sprang, as shown in 
figure 3 } and in prepared sections (fig. +d), from the portion of the side imme- 
diately adjacent to the back ; and consisted in that position almost solely of tubes 
of nearly full transverse dimensions. Lastly, the tubuli composing the perfected 
sides and axillz ot the branches, presented no indications of intermediate sizes. 
From these statements it is believed, that though structurally identical except in 
diameter, the two sets of pores or tubes were permanently occupied by portions 
of the polype, which performed essentially distinct functions. 
With regard to genera which are furnished with two series of apertures, the 
nature of the subordinate set in Heteropora is doubtful. Some of the typical 
species, as Het. cryptopora' and H. anomalopora’, possess apparently pores of 
every intermediate size ; and the same may be said of H. conifera® and H. du- 
metosa*, while H. dichotoma® exhibits, as delineated, two very distinct sets. 
Whatever may be the true nature of those openings, or of the structures con- 
nected with them, the depictured characters convey no idea of tubuli inclined 
against the surface of the branch, a marked property in the cretaceous fossil. 
M. Michelin has placed in the genus Ceriopora®, a coral which has also two sets 
' De Blainville, Man. d’Actinol. p. 417; Goldfuss, Petref. Ceriopora eryptopora, tab. 10. f. 3. 
* Ibid. Ibid. tab. 10. f. 5. : 
* Milne-Edwards, Lamarck, ed. 1836, t. ii. p. 318; also Lamouroux, Millepora conifera, Exposi- 
tion Méthodique, tab. 83. figs. 6, 7. 
* Lamarck, edit. 1836, t. ii. p. 317 ; Lamouroux, tab. 82. figs. 7, 8. ° De Blainville, op. cit. p. 417. 
* Iconog. Zoophytol. p. 124. pl. 32. fig. 7. 
