108 MADREPORARIA. 
93. Porites Bay of Panama ql, (P. Panamensis prima.) (Pl. X. fig. 3.) 
[Panama and Pearl Islands,* coll. F. H. Bradley ; Yale College Museum and British Museum. | 
Syn. Porites Panamensis Verrill, Proc. Boston Soc. Nat. Hist. x. (1866) p. 329. 
Description.—The corallum is encrusting, thickening in the centre to a mound; stocks 
from 10 to 15 cm. across show a thickness of 1*2 to 3°6 cm. The surface is convex, irregular, 
and uneven. 
The calicles are small, 0°75 mm., crowded, a little excavate, rather shallow but distinct ; 
the walls rather thin, roughly granulous, porous, but firm. 
The septa are well developed, narrowed and somewhat thickened outwardly, the sides very 
thickly covered with coarse, rough lacerate granules, the edges also rough and lacerate. Pali 
small and rather stout, roughly lacerately granulous. The columella is small, inconspicuous, 
and often wanting. 
The colour of the unbleached corallum is dark ash brown. 
This is Professor Verrill’s description, to which is added the fact initialled by the collector 
(see Trans. Conn. Acad. i. part 2 (1867-71) p. 505) that the polyps when expanded “are exsert, 
with twelve equal, cylindrical, light-brown tentacles, not swollen at the tips, which are white.” 
There are fortunately two specimens in the British Museum also from Mr. Bradley’s 
collection; they show the corallum closely adherent and without free edges. The irregu- 
larities of the surface are largely due to foreign organisms, e.g. Balanids, and the edges have 
very irregular outlines, putting out processes there, cut here into bays. 
The calicles are irregular in size, and the walls very irregular in thickness. The details 
of wall formation are difficult to unravel owing to a woolliness of the surface. When they. 
are thin there is a tendency to form a simple zigzag trabecular wall, from which the septa, 
thickened and roughened by fine spiky frosting, project into the calicles. Where they are thick 
they are raggedly reticular without trace of formal structure, but running out in all directions 
into thick frosted points. Near the aperture of the calicle the septa are short and free; the 
typical fusions can, however, be dimly made out deep down in the fossa, and five pali can be made 
out also spinously frosted. This frosting obscures the details of the intra-calicular skeleton, 
which, however, seen from above, is symmetrically radiate. The pali form a compact ring and 
are not conspicuous; they are more distinct, however, in the shallower calicles upon the thin 
expanding lobes of the edges. 
There can be little doubt that these two specimens belong to the same form as that 
described by Dr. Verrill; the figure here given and these additional details were required to 
bring our knowledge of it up to date. 
Both the specimens are greyish-brown, with whitish bloom over them, due to the hairy 
frosting, which is very remarkable. 
a, b. Zool. Dept. 7. 8. 22. 18. 
The other form from Pearl Islands described by Dr. Verrill as Porites excavata is a Goniopora. 
* In rocky pools, and in patches just below low-water mark, the specimens may be sub-globular 
if they encrust small pebbles. 
