A monograph of the British fossil corals - kreidefossilien.de
A monograph of the British fossil corals - kreidefossilien.de
A monograph of the British fossil corals - kreidefossilien.de
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62 BRITISH FOSSIL CORALS.<br />
C. cylindrica, C.Breda, and C'.Koninckii, have only six large j!?«/«, whereas in C. Bowerhanlcii<br />
<strong>the</strong> number <strong>of</strong> <strong>the</strong>se organs amounts to twelve. C. Iccvigata^ differs from <strong>the</strong> above<strong>de</strong>scribed<br />
species, by <strong>the</strong> pali being narrow, and very thick, and C. Beheyana by <strong>the</strong><br />
existence <strong>of</strong> a well-marked epi<strong>the</strong>cal band near <strong>the</strong> calice.<br />
M. Alci<strong>de</strong> d'Orbigny has, in a recent publication," referred to this species as <strong>the</strong> type<br />
<strong>of</strong> his new genus Jmbloci/afhus, which he <strong>de</strong>fines as being Cyatlnna, with a circular calice<br />
and a round columella. He adds that Amblocyathus is a lost genus, and contains three<br />
<strong>fossil</strong> species belonging to <strong>the</strong> Neocomian and Albian^ strata. We must, however, beg<br />
leave to remark, that <strong>the</strong> two above-mentioned characters are met with in almost every<br />
species <strong>of</strong> our Cyathina, and most especially in C. ci/afJius, which is <strong>the</strong> type <strong>of</strong> <strong>the</strong> genus<br />
Cyatlnna, and is actually living in <strong>the</strong> IMediterranean sea. Only two <strong>of</strong> <strong>the</strong> species<br />
referred to <strong>the</strong> genus Cyathina in our ]\Ionograph ' <strong>of</strong> <strong>the</strong> Turbinolidse' present a slightly<br />
oval calice and a transversal columella C. 2}seudoturbinoKu and C. Guadulpensis. In<br />
C. SmitJiii <strong>the</strong> columella is oblong, but <strong>the</strong> calice is circular, or nearly so. If it be con.<br />
si<strong>de</strong>red necessary to separate <strong>the</strong> Cyathina with a circular calico from those that have an<br />
oval calice, it would <strong>the</strong>refore be more proper to give a new generic name to <strong>the</strong> latter, and<br />
not to change <strong>the</strong> <strong>de</strong>nomination <strong>of</strong> <strong>the</strong> group containing <strong>the</strong> very species for which<br />
Ehrenberg first established <strong>the</strong> genus Cyathina. But this innovation, proposed by<br />
M. d'Orbigny, appears to us as being in every respect unnecessary, for <strong>the</strong> slight <strong>de</strong>formation<br />
<strong>of</strong> <strong>the</strong> calice and <strong>the</strong> columella which forms <strong>the</strong> sole basis <strong>of</strong> <strong>the</strong> new generic division, can<br />
hardly be consi<strong>de</strong>red as characters <strong>of</strong> sufficient value; species that differ in no o<strong>the</strong>r<br />
respect are <strong>of</strong>ten found to vary in this way, and even specimens belonging to <strong>the</strong> same<br />
species sometimes differ much in <strong>the</strong> form <strong>of</strong> <strong>the</strong> calicular margin. Thus, although <strong>the</strong><br />
calice is circular, or nearly so, in most specimens <strong>of</strong> C. cyathis and C. Sniif/iii that are met<br />
\nth, we have seen some that were compressed, and had <strong>the</strong> calice as oval as in C. pseudoturhinolia<br />
and C. Guadulpensis ; similar <strong>de</strong>viations from <strong>the</strong> normal form are also to be<br />
met with in <strong>the</strong> columella; in C. SniUJiii, for example, this organ is sometimes quite<br />
circular, although it is in general oblong. Differences <strong>of</strong> this kind, when not more marked<br />
than is <strong>the</strong> case among <strong>the</strong> various species <strong>of</strong> Cyathina, can <strong>the</strong>refore scarcely be <strong>de</strong>emed<br />
important enough to characterise generic divisions ; and, as in <strong>the</strong> present case, <strong>the</strong>y do<br />
not appear to coexist with any o<strong>the</strong>r structural peculiarity, we see no reason for admitting<br />
<strong>the</strong> new genus Amblocyathus.<br />
1 Tab. ix, fig. 1.<br />
2 Note siir <strong>de</strong>s Polypiers Fossiles, Paris, 1849.<br />
^<br />
M. d'Orbigny eniploy.s <strong>the</strong> name oi Albiuti formation to <strong>de</strong>signate <strong>the</strong> Gault.