APPENDIX A. (LONSDALE ON CORALS.) 
623 
an axis ; nor did they occur in a specimen, so worn down by the describer that the centre could not be 
passed, and an axis exist, without being discovered. In some of the Bristol longitudinal sections, how- 
ever, displaying in all other respects a perfect agreement with those of the Kamensk fossil, a central body 
was occasionally more or less developed, and when fully, it resembled so greatly the axis of true Lithodendra, 
that a generic identity might have been inferred. It is believed, nevertheless, that there are important es- 
sential differences between the apparent axis of the proposed genus and the real axis of the established one. 
In Lithodendron it forms a marked persistent body, variously constituted, but ranging continuously through 
the centre of the stem, and forming in the terminal cup a bold boss : there is also no connexion between 
it and the mode of ramification, the branches springing from the side, and being in no way influenced by 
it. In the proposed genus, on the contrary, the central body varies in characters, the variations depend- 
ing, it is believed, on the manner in which the ramifying was effected. In longitudinal sections of both 
Kamensk and Bristol specimens, an acicular point, more or less prolonged, was not unfrequently noticed 
springing vertically or obliquely from the centre of one diaphragm, and occasionally ranging to the under 
surface of the next. In some sections from Bristol, not those which exhibited most strongly the appa- 
rent axis, similar acicular lines traversed two, or more, successive intervals, but without any regular con- 
nexion, the terminations on the upper and under sides of the diaphragms not coinciding in position. Be- 
tween these intersected intervals, others occurred in which no central process was noticed. Again, in lieu 
of a single line, two occasionally appeared springing obliquely from a continuous base or diaphragm, and 
were united in an acute angle, either at the top of the interval, or after extending through more than 
one, and in such cases interrupting the range of the intermediate diaphragms. Occasionally also one of 
the transverse laminEe was bent upwards at an obtuse angle in the centre. In the most strongly charac- 
terized axes, the diaphragms were in general very irregular, and sharply inclined against the central aci- 
cular line ; the whole agreeing, as before stated, almost perfectly in appearance with the axis of some 
true Lithodendra. All these structures were very unequally exhibited, and even the last was preceded 
and succeeded in the same section, which showed no distinct curvature, by regular diaphragms and in- 
tervals, without any indications of a central body. In nearly 300 transverse or oblique sections, displayed 
in polished Bristol slabs, no true axis was observed ; and in the only terminal cup examined (a Kamensk 
specimen), no boss was discovered, during a careful removal of the sediment with which the depression 
had been filled. 
It is proposed now to state briefly the conceived real nature of these various central structures, and to 
point out in what respects they are believed to differ from the axis of Lithodendra. 
The branching in the corals under consideration, was effected by a perfect medial subdivision of the stem, 
and consequently in the exact range of the indications above noticed of irregularities in the inhabiting 
polype : moreover, those structural inequalities often immediately preceded the sub-divisional process, and 
could easily be referred as the first steps in that new order of growth which was speedily perfected in the 
divided branches. In figure 4 b, Plate A., an acicular line immediately precedes the bifurcation : and the 
reader is requested to compare the oblique, subdivided diaphragms at the commencement of the separated 
branches with the inclined plates mentioned above. It is therefore inferred, that all the irregularities or 
apparent axeal structures are but immature signs of the process which was effected at the fitting period ; 
and further, that such a mode of branching precluded the existence of a persistent axis similar to that of 
Lithodendron: it has been already stated, there is no connexion in that genus, in position or otherwise, be- 
tween the axis and the lateral offsets or branches developed from germs. According to Ehrenberg, this dif- 
ference in the mode of ramification demands not only a generic separation, but tha tne coral should be 
placed in a distinct family from that to which Lithodendron belongs. 
4 L 2 
