DESCRIPTION OF CHALK CORALS. 319 
exterior was in one condition membranous, the calcareous matter was, it is 
conceived, successively added in a similar manner, though in neither case always 
continuously, faint indented lines being sometimes detectable within the area. 
By whatever means the covering was formed, the construction of the distal pro- 
tuberance (fig. 8 b), representing it is believed the aperture, appears to have been 
simultaneously effected, as no open space marking a mouth was noticed. At 
first these small swellings were suspected to be ovarian capsules, but on carefully 
laying one of them open, no distinct chamber appeared beneath, similar to that 
represented in fig. 8 b+, which is regarded as a true capsule ; and on removing 
the remainder of the covering, the whole interior was found to be a simple cell. 
They were small and often difficult to detect, the best-defined being a segment of 
a circle ; such examples also consisting frequently of casts of the external lamina. 
In all cases they were surrounded by a faint furrow, and occasionally a minute 
central pore could be detected. The foramen near the middle of the exterior of 
the cell (fig. 8a) occurred very generally, but varied in form, being circular, oval 
or elongated, also narrow, resembling a slit ; and occasionally two foramina were 
visible, one being situated close to the distal protuberance. Figure § b + repre- 
sents what was considered an ovarian capsule. The position of the little chamber 
is clearly without the cell to which it belonged, having its own boundary, but a 
channel of communication apparently existed at the upper extremity of the cell. 
Flustra ? inelegans. (Tab. XVIII. B. figs. 9, 10, 11.) 
Incrusting or in free lobes composed of two opposite layers structurally 
united ; outline of cells pear-shaped, truncated at the proximal extremity, bound- 
ary a projecting ridge intimately united in adjacent cells ; surface wholly exposed, 
flat or very slightly convex ; aperture at distal end, semicircular with a raised 
margin, and generally a notch at each extremity of the straight side ; ovarian 
capsules semicylindrical, situated partly over the mouth of the cell and concealing 
it, entrance semicircular, edge sharp ; exterior of the cells unaltered by age. 
The fossil represented by figs. 9, 10,11 (Tab. XVIII. B.) possesses in the complete 
exposure of the range of the cell, the raised, united margins, flattened surface, and 
to the extent observed, in the unchanging exterior, the characters of true Flustre ; 
while it differs in these particulars, especially the last, from Eschare. The in- 
crusting in addition to the free mode of growth, affords a further agreement with 
the former genus ; and if Eschare be constantly free, except at the base, and 
always formed of two layers, another distinction between them and the chalk 
212, 
