GENUS CALCABINA: EXTEENAL CHAEACTEES. 549 



the Eocene Tertiaries of France, has been described by D'ORBiGNY* under the name of 

 Eotalia armata, and by DssHAYEsf under that of Calcarina rarispina. 



195. The following is the character of the genus Calcarina given by M. D'ORBIGNY 

 in his ' Foraminiferes 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 contre 1'avant dernier tour de spire. Semblable aux Rotalines 

 par son enroulement spiral, par ses deux cotes a peu pres aussi convexes, par 1'emplace- 

 ment de son ouverture, ce genre s'en distingue par les tres longs prolongements exterieurs 

 de son pourtour, appendices singuliers qui font supposer, dans 1'animal, un mode de 

 secretion tout particulier." OfSiderolina he says (p. 116) : " Coquille libre, equilaterale, 

 orbiculaire, encroutee en dehors, composee d'une spire embrassante a tous les ages, 

 ayant des appendices allonges au pourtour, interrompant, dans 1'interieur, la suite des 

 loges. Ouverture contre le retour de la spire toujours masquee a la derniere loge. Les 

 Siderolina se distinguent des Nummulina par les appendices du pourtour, qui, dans 

 1'interieur de la coquille, viennent 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- 

 mary 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 ForaminiferaJ" ; 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 Polystomellce 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. torn. vii. p. 273, No. 22 ; and Modeles, No. 70. 

 t Lyell's Manual of Geology, 5th ed. p. 228, fig. 236. 

 | Annals of Nat. Hist., Ser. 3. vol. v. p. 174. 



