G20 
APPENDIX A. 
(LONSDALE ON CORALS.) 
with the occupants of surrounding columns. In Lithostrotion floriforme, on the contrary, as already stated, 
there is no tendency to divide naturally on all sides, the walls being essentially “ coadunated,” a character 
alluded to by Martin in his account of the fossil ; and though he says that " they are in most specimens 
separable,” yet such natural divisions have been found to be only occasional and confined to a limited part 
of the exterior of the columns, the other portions being firmly united. These separations are believed to 
occur only where two groups of columns have been irregularly brought in contact. (Petri. Derb. descrip- 
tion of pi. 43 and 44, referred to by Dr. Fleming, Brit. Anim. p. 508.) Internally Lhwyd’s or the Bristol 
coral is divisible in the mature state into two areas, not three: — 1st, a centre more or less extensive, 
occupied by lamellae variously blended or by contorted laminae, but not traversed by a distinct, persistent 
axis ; and - 2ndly, an outer area intersected by vertical persistent lamella:, the interstices being variously 
crossed by inclined or arched vesicular plates. The additional columns were produced by a subdivision 
parallel to one of the facets of the pre-existing column, and not by the development of a circular germ. 
Externally, the partition was rendered visible by a line commencing in outer walls on opposite sides of a 
column, and ranging upwards, it almost immediately marked a clear boundary between two distinct 
columns. The polypes which inhabited these structures formed, as before stated, independent, adjacent 
walls, and had, it is inferred, no connexion at the upper extremities. To this mode of production, the 
facility with which the columns are detached is necessarily ascribed. In Lithost. floriforme the germ pro- 
duced within the area of the parent was circular, its periphery having no parallelism with the sides ot the 
previous column, and it did not devclope a separate wall, the boundary between the young and the old 
columns having been a conjoint labour. It may he also stated, that the aptitude of the polj pes to fill 
every inequality due to growth, precluded the possibility of the introduction of interstitial columns. 
The internal characters dependent upon this manner of reproduction were better exhibited in a Russian 
coral, described in the next page, than in the Bristol fossil, but they are briefly noticed here to complete, 
as far as possible, the generic memoranda. In a section, purposely made, about half a line below the 
point, where a subdivision was visible, the transverse under surface exhibited not the least sign of any 
irregularity in the lamellce or in the interstitial plates. The young or offset column, which commenced im- 
mediately above the section (PI. A. fig. 2 b), nearly subdivided the facets from which it sprung, but its area 
was much less than half that of the pre-existing column. The exposed surface was inclined obliquely for- 
ward, and therefore did not display everywhere an equal state of development. The structure exhibited in 
this uneven plane was much less regular than that in the section beneath, though not very different from 
the arrangement of the component lamina: near the sides of other columns in which no subdivisions existed : 
traces also of extension upwards of the lamella: of the undivided column were likewise detectable, indicating 
that the polype of the young column possessed, to a certain extent at least, the secreting membranes of 
the old. It must also be stated, that though irregularities in the exterior of the columns attended in 
some cases the production of the offset, yet that in others there was no disconnection upwards between 
the ribs of that portion of the undivided wall which was subjacent to the young column, and those on the 
surface of the latter. In every instance in the Russian specimen as well as in the English the divisional 
line of the offset was parallel to one of the facets, and the youngest condition of the severed portion was 
an irregular polygon. In Lithostrotion, the lamella: of the offspring could not be referred even in part to 
a continuation with pre-existing structures. 
In all respects, therefore, it is believed that the Bristol, and consequently Lhwyd’s coral, is generically 
distinct from Dr. Fleming’s Lithostrotion floriforme. 
In the inferred mode of producing additional columns, there is a resemblance to the fossiliferous opera- 
tion characteristic of the Astrea and Favia of Ehrenberg as well as of the restricted Caryophyllia of the 
same authority. In the two former however the polypes belonging to one specimen possess a perfect 
