A monograph of the British fossil corals - kreidefossilien.de

64 BRITISH FOSSIL CORALS.
of unequal size towards the calicular edge. Calice almost circular, or somewhat oval aud
shallow. Columella fascicular, well developed, not prominent at its apex, and terminated
by ten or fifteen papillae of equal size. Sqita forming four complete cycla and six wellmarked,
equally developed systems, in which, however, the secondary ones differ but little
from those of the first cyclum. The septa are slightly exsert, closely set, unequal, and
rather thicker outwards than towards the columella. Pali narrow and unequal; those
corresponding to the tertiary septa broad and rather stout ; the others, and most especially
those corresponding to the primary septa, narrow and thinner. Height of the corallum,
seven or eight lines ; diameter of the calice, almost seven lines.
This species belongs to the first section of the genus Trochoeyathus {T. simjjlices), and
diifers from T. impari-2Mrtitus^ and T. BeUh)(jlienanus by not having a fifth cyclum
of septa ;
its general form distinguishes it from T. mitratus,^ T. crassus, T. simjjlew, and
T. costulatus, -which are all short, broad, and curved ; and from T. elongatm, T. Komnckii,
and T. gracilis, which are much elongated, curved, and very narrow towards the basis.
It
appears to resemble most, especially by its general form, T. ciqnda^ which is also conical
and straight, but this last-mentioned species differs from it by the thickness and strong
granulations of the septa, and by the breadth of the basis.
Trochocyatlms conulus appears to have been very widely spread in the seas where the
Gault formations were deposited.
The specimens which we most particularly studied were
'
See our Monograph of Turbinolidse, loc. cit., p. 30".
- Since the publication of our Monograph of the Turbinolidee (in 1848) we have recognised that the
fossils from Tortona, which M. Michelotti designates under the name of TurbinoUa pHcata, do not differ
specifically from the specimens existing in the Poppelsdorf Museum under the name of Tiirliinolia mitrata,
Goldfuss. As we already expected, the latter specific name must therefore be substituted for the one
employed by M. Michelotti, and M. Michelin.
' This new species, designated under the name of TurbinoUa cujmla, by M. Alex. Rouault, (Bulletin
de la Soc. Geol. de France, 2""' serie, vol. ix, p. 206, 1848), was found by that geologist at Bos d'Arros, in
the department of the Lower Pyrennees, and does not appear to differ from a fossil which exists in the
collection of M. Nyst, and was found in the Eocene formation at Lacken, near Brussels. Ti-ochoctjathus
cvimla belongs to the first section of our genus Trachocyathus, and presents the following characters :
Corallum straight, or almost so, subturbinate, but short, and having a broad peduncle, but not remaining
adherent in the adult state. Costca distinct from the basis, straight, unequally developed alternately,
rather prominent, especially near the cahce, granulated and striated transversely ; rudimentary costse, that
do not correspond to any septa, are seen in the intercostal furrows. Calice circular; fossula not deep.
Columella crispate, well developed. Septa forming three complete cycla, and in general a fourth incomplete
cyclum in one half of three of the systems ; exsert, rather unequal, strong, and presenting on their
lateral surfaces large prominent granulations, which are arranged in lines nearly parallel to the upper edge.
Pali thick, strongly granulated, and unequal ; those corresponding to the tertiary septa the largest in the
half sj'steras where the septa of the fourth cyclum exist, and those corresponding to the secondary septa
most developed in the other part of the calice. Height of the corallum, three lines ; diameter of the calice
almost as much. By the strong granulations of the septa, and the breadth of its basis, this species tends to
establish a transition between the genus TrocJiocyatJuis and the genus Paraeijathus.