GENUS CALCAEINA: — ^EXTEENAL CHAEACTEES. 
549 
the Eocene Tertiaries of France, has been described by D’Okbigny* under the name of 
Rotalia armata, and by DESHAYEsf under that of Calcarina rarispina. 
195. The following is the character of the genus Calcarina given by M. d’Orbigny 
in his ‘ Foramiiiiferes Fossiles de Vienne’ (p. 160). “ Coquille libre, spirale, deprimee, 
tres rugueuse, formee d’une spire enroulee sur le cote, entierement apparente en dessus, 
embrassante en dessous, composee de loges prolongees en appendices marginaux, souvent 
tres allonges, representant, dans leur ensemble, comme la molette d’un eperon. Ouver- 
ture en fente longitudinale centre I’avant dernier tour de spire. Semblable aux Rotalines 
par son enroulement spiral, par ses deux cotes a peu pres aussi convexes, par I’emplace- 
ment de son ouverture, ce gem’e s’en distingue par les tres longs prolongements exterieurs 
de son pourtour, appendices singuliers qui font supposer, dans I’animal, un mode de 
secretion tout particulier.” Of Siderolina he says (p. 116) : — “ Coquille libre, equilaterale, 
orbiculaire, encroutee en dehors, composee d’une spire embrassante a tons les ages, 
ayant des appendices allonges au pourtour, interrompant, dans I’interieur, la suite des 
loges. Ouverture centre le retour de la spire toujours masquee a la derniere loge. Les 
Siderolina se distinguent des Niimmulina par les appendices du pourtour, qui, dans 
I’interieur de la coquille, rdennent interrompre la suite des loges obligees de passer de 
chaque cote.” No mention is made of Calcarina in M. d’Orbigny’s most recent sum- 
maiy of the classification of the Foraminifera (Cours Elementaire de Paleontologie), 
this genus not being regarded by him as occurring in the fossil state ; but he repeats 
his characterization of Siderolince as Nummulites the turns of whose spire are inter- 
rupted by testaceous appendages. It will presently appear that the conception which 
M. d’Orbigny has formed of the structure of this type is erroneous in so many particulars, 
that without the assistance of figures and models it could not be recognized by the generic 
characters which he has assigned either to Calcarina or to Siderolina. 
196. A very correct general description of the structure of Calcarina has recently been 
given by Messrs. W. K. Parker and T. R. Jones, in their valuable series of papers on 
the “ Nomenclature of the Foraminifera ; but their information in regard to it having 
been almost entirely based on external characters, and their description being altogether 
deficient in those minuter details which it is my special purpose to record, a full account 
both of its internal structure and of the principal varieties of its external configuration 
will not be the less valuable to those who may have occasion to study this type. 
197. External Characters. — The comparison of the form of this organism to that of 
the rowel of a spur sufficiently well characterizes the general aspect which it ordinarily 
presents, as shown in Plate XIX. figs. 1-4. The feature which most distinguishes it 
from other Helicostegue Foraminifera (only some Eotalice and Polystoniellce presenting a 
slight approximation to it in this particular) is the presence of a set of rays or spines, 
variable alike in number, length, and direction, which diverge from the central disk. 
* Ann. des Sci. Nat. tom. Tii. p. 273, No. 22 ; and Modeles, No. 70. 
t Lyell’s Manual of Geology, 5tli ed. p. 228, fig. 236. 
f Annals of Nat. Hist., Ser. 3. vol. v. p. 174. 
