Chap. X.] 
UPPEK SILUEIAJS T COEALS. 
221 
through this marginal ' calicular ' development ; and this process is frequently- 
repeated in the upward growth of the Coral. (See the larger figure.) 
Another species, so like the former that in some conditions it might easily be mis- 
taken for it, is Acervularia ananas (A. luxurians, Eichwald), described by Linne * 
and Fougt from rocks in Gothland which are now known to be Upper Silurian. 
A single cup is represented (Foss 54. f. 6), which has given birth, by fissiparous 
division, to four young corallites, which take their rise, not from the margin, but 
from the centre of the old Coral, the life of the parent being thus continued in 
the offspring. (See Lonsdale in ' Sil. Syst.' pi. 16. f. 6.). As a number of these 
buds grow up together, they stunt each other's growth in a lateral direction ; and 
as the process of multiplication is often repeated, the corallites by mutual pressure 
are forced into an angular form like the cells of a honeycomb ; their edges grow 
together, and the result is a compound mass of stars f . (See the right-hand 
figure.) 
There are several other Cup-shaped Corals which are frequent in the upper 
division, and especially in the Wenlock Limestone ; but they are not so charac- 
teristic as those just mentioned: — Omphyma turbinata, Linn., 0. Murchisoni, 
Milne-Edw., Cystiphyllum cylindricum, Lonsdale, C. Grayi, Milne-Edw., and 
C. brevilamellatum, M'Coy ; Cyathophyllum angustum, Sil. Syst. pi. 16. f. 9, C. 
trochiforme, M'Coy, Strephodes vermiculoides, Foss. 54. f. 3 (Strombodes dif- 
fluens, Milne-Edw.), Ptychophyllum patellatum, Foss. 53. f. 5 (a remarkable 
species, in which the elevation of the centre of the cup is so great as to give the 
Coral a reversed appearance, the base being nearly flat), Clisiophyllum vortex, 
M'Coy, and Goniophyllum Fletcheri, M.-Edw., a four-sided Coral, very like one 
found in the Isle of Gothland, Sweden. Some Cup-corals also are common to 
Gothland and Britain, such as Aulacophyllum mitratum, Hisinger, and Cyatho- 
phyllum Loveni, M.-Edw., besides the two species of the latter genus before 
mentioned X j and there are some which extend their range to America. 
The Ludlow rocks, being for the most part mudstones, do not often contain 
many Corals ; but in their calcareous portions one or other of the species above 
described occur §. Prof. M'Coy has added Cyathaxonia Siluriensis to the scanty 
Ludlow list ; it is from Kendal. Favosites fibrosus, Goldf., indeed, is very com- 
mon in the form of an incrusting envelope upon the spiral shells Cyclonema and 
Murchisonia (see p. 132 and p. 119, Foss. 18. f. 8). Together with Favosites 
asper, d'Orb., and some few others, it seems to have been indifferent to the 
nature of the sediment it lived upon ; they are found throughout the system. 
The little Paleeocyclus appears to have lived indifferently on a calcareous, muddy, 
or gravelly bed. Petraia bina seems to have preferred a muddy habitat ; but most 
species of this genus are chiefly found in sandstones ||. 
Note. — On the 'Zoantharia rugosa,' and their operculated forms in particular, G. 
Lindstrom, Ph.M. of Wisby, Gothland, thus writes (CEfversigt af Vetenskaps Akad. For- 
handlingar, 1866 ; and Geol. Mag. 1866) : — " Professor Steenstrup some years ago ques- 
tioned the fact as to whether the Zoantharia tabulata and Z. rugosa, included by him 
* Amcenitates Academic*, vol. i. p. 196 &c. figured by Hisinger. 
t The growth and reproduction of Corals has § This relation of Corals to Limestone is one of 
of late years been much studied, and well illus- the facts most prominently shown in the very va- 
trated by Dana, Milne-Edwards, Fromentel, Mi- luable Tables of the relationship of the organic re- 
chelotti, Duncan, and other naturalists. mains and sedimentary materials of the Silurian 
I So many of the Wenlock Corals are found in rocks both of North America and Wales, in Dr. 
the limestone of Gothland in the Baltic, that the Bigsby's elaborate memoir on the distribution of 
stratum might have been identified by them alone the rocks and fossils of the Palaeozoic area of New 
— Heliolites interstinctus, Favosites alveolaris, F. York State, compared with that of Wales and 
Gotlandicus, F. cristatus, Ccenites juniperinus, other regions. Quart. Journ. Geol. Soc. vol. xv. 
Halysites catenularius, Syringopora fascicularis, p. 295. 
Omphyma turbinata, Ptychophyllum patellatum, || See also Dr. Bigsby's Tables of fossils and 
Acervularia ananas, &c. These species are well sediments referred to above. 
