214 Mr. R. Etheridge and Dr. H. A. Nicholson 
interior; and similar pores are very often found in a very well- 
marked form on the lower surface of the colony. Though 
abundant on the margins of the cups, the pores seldom extend 
into the interior of these depressions; and the bottom of the 
cups does not appear to be ever perforated by pores. In 
other specimens, again, the surface appears to be destitute of 
the large pores just mentioned; but in all alike the general 
surface, as examined under the microscope, shows a spongy 
and minutely porous aspect, though it is difficult to determine 
positively whether this be really due to the presence of ex- 
tremely fine pores or not. 
In the interior of the cups the tubercles and vermicular 
ridges often have a distinctly linear arrangement, radiating 
from the centre of the cup, and form the so-called “ septa.” 
They certainly present a close resemblance to the septal striz 
of many forms of Cystiphyllum, and a less close one to those 
of Protarea; and if Paleacis is a true coral, they doubtless 
represent the septa. On the other hand they present an 
equally close resemblance to the surface-tubercles and vermi- 
cular ridges (also often in parts radiate) of various Stromato- 
poroids ; so that little weight can be attached to this as de- 
ciding their true nature. In his figure of P. cunetformis 
(Hist. Nat. des Cor. vol. i. pl. E.1. f. 26) Milne-Edwards 
figures a principal pair of septa, placed opposite each other, as 
a longitudinal ridge dividing each cup into two halves. In his 
description of the species, however, he speaks of these septa 
with much doubt and hesitation, stating that the cups “‘parais- 
sent avoir été partagés par deux grands cloisons, dont on ne 
voit plus que des traces fort obscures dans la direction de l’axe 
vertical du polypier.”” Prof. de Koninck appears to have 
regarded the pair of principal septa with much suspicion ; and 
we can safely assert that they are not present in any example 
examined by us. ‘The tubercles or papille forming these so- 
called septal strie vary in size in the same individual, and 
even in the same line or septum. In all cases those occu- 
pying the floor of the cups are irregularly scattered, and do 
not appear to be arranged in any definite manner. 
Micro-structure.—The intimate structure of Palwacis does 
not hitherto appear to have been investigated by means of 
thin sections prepared for the microscope. Our researches in 
this direction have been confined chiefly to P. cyclostoma 
(Pl. XII. figs. 7, 8), of which our material was most abun- 
dant, though we have also made a few sections of P. cuned- 
formis (Pl. XII. fig. 14). In the former of these two species 
the minute structure of the organism, as displayed by this 
method of examination, is as follows (Pl. XII. figs. 7, 8) :— 
