GRABAU : MONILOPORIDAE. 
415 
is probably due to the method of preservation; nevertheless, this 
feature indicates what is probably the true relation between the 
trabeculae and the walls. The former appear to be local elevations 
of the latter, or, again, the walls appear as if formed by the lateral 
expansion of the bases of the trabeculae. This relation of the 
lamellae of the wall to the trabeculae is well shown in the cross- 
sections of C. jacksoni (PI. 2), where the lamellae are seen to bend 
inwards to form the trabeculae. 
The trabeculae are commonly short, usually projecting only part 
way across the lacunae, but occasionally they are long enough to 
project across from wall to wall, thus presenting, on a larger scale, 
the character seen in Monilopora. More rarely a trabecula projects 
beyond the next added lamella, which then envelops it with an 
additional layer of sclerenchyma (PI. 2, fig. 9). 
In the calices, the trabeculae are arranged in parallel vertical 
rows, of which from sixteen to twenty have been counted in differ¬ 
ent specimens of C. distorta. In the procumbent portion of C . 
dichotoma , the rows of trabeculae gradually diverge, new ones 
coming in between, until they reach the calyx, where they are 
disposed in parallel vertical rows (PI. 3, fig. 14). At the bases 
of the new corallites the trabeculae are especially numerous, pro¬ 
jecting from all sides across the pore connecting the bud with the 
parent. In old individuals of C. dichotoma , and in adult individ¬ 
uals of C. distorta , the trabeculae cover most of the pore. In C. 
distorta the orifice becomes closed over during the course of further 
growth, the polypites thus becoming separated. After this, the 
wall thus formed is commonly thickened by the addition, on both 
sides, of new layers of sclerenchyma. This separation of originally 
conjoined polypites probably takes place in C. jacksoni, although 
it has not been observed. In C. dichotoma , the polypites appar¬ 
ently remain united throughout life. 
Ceratopora jacksoni, sp. nov. PI. 1, fig. 1. PI. 2, figs. 6-10. 
Description. Coralliun erect, frequently and irregularly brandl¬ 
ing; corallites cylindrical, or slightly trumpet-shaped. Surface 
formed by a coarsely wrinkled epitheca, and showing longitudinal 
ridges or costae. Cavity of the calyx funnel-shaped, continued as a 
cylindrical central tube, which seldom occupies more than one third 
of the diameter of the corallite. Cysts coarse, irregular, arranged 
semi-concentrically, with frequent spine-like processes or trabeculae 
projecting from the lamellae of the wall. 
