•iGJ FAMILY NUMMULINiDA. 



perceive the strongly marked difFei-ences that exist between Niimmulites and the ordinary 

 siphoniferous Cephalopods ; and he regarded them as internal shells, completely enclosed (like 

 Spiri/Ia) within the animal, instead of giving lodgment to its body in its own chambers. In 

 this view he was followed by Deshayes and Defrance (xxix). 



454. It was in 1825 that the Nummulites were detached by D'Orbigny (lxix) from the 

 siphoniferous chambered shells, and ranged with the minuter shells then first distinguished 

 by the term Foramiiiifera ; still, however, being considered to belong to the class of Cephalo- 

 poda. The Lamarckian designation Numnmlites was altered by D'Orbigny to Numnmliua, on 

 the ground that the genus had existing representatives; the genus LrnticnUte^: was not 

 adopted, having been previously shown to be untenable ; but a new genus JsnUiua was 

 created for the reception of those forms in which the investment of the earlier whorls bv the 

 later is incomplete, so that the turns of the spire are partially apparent, — a distinction which 

 we shall presently find to be of no essential importance. His description of the Nuramulitic 

 type was extremely inexact ; and the first approach to a more precise account of it was given 

 by Sowerby in his 'Mineral Conchology' (1829), who accurately described and figured the 

 true aperture of communication between the chambers (which does not seem to have been at 

 that time recognised by M. D'Orbigny), and traced the alar prolongations of the septa from 

 the peripheral margin towards the centre on either side. Numerous dissimilar forms of 

 Nummulites were subsequently brought to light by the researches of geologists in various 

 localities ; but for some time no essential advance was made in the knowledge of their struc- 

 ture ; and the discovery of M. Dujardin in regard to the Rhizopod character of the animal of 

 Foraminifera generally does not seem to have been applied to this particular type, until 

 MM. Joly and Leymerie applied themselves to the investigation of its conformation. Their 

 Memoir (liii), published in 1848, brought together most of the results attained by previous 

 inquiries, which were confirmed by their own researches ; but they did not discover any 

 new points of importance, — the chief novelty which they announced having been previously 

 put forth by M. de Keyserhng,* though probably without their knowledge. According to 

 these observers, the spiral lamina of Nummulites is perforated with large apertures, the con- 

 tinuity of which through successive layers forms canals reaching from the median plane to the 

 surface on either side ; these canals are filled up in the process of fossilization by calcareous 

 infiltration ; and the projection of the ends of the columns thus formed, from the surface 

 of specimens that have l^een subjected to attrition, gives rise to the granulations often 

 observable thereon. The inquiries into the minute structure of Nummulites on which I was 

 myself at that time engaged led me to the same view, without any knowledge that it had been 

 previously arrived at ; and having found myself fortified by the concurrence of MM. Joly and 

 Leymerie (with whose researches I became acquainted before the pubhcation of my own"), I 

 expressed it without hesitation (xii, p. 26) in the Memoir which contained the results of m)* 

 carliest researches into the microscopic structure of Foraminifera. It was from the first 

 opposed, however, by Prof. Williamson and Mr. T. Rupert Jones, wdio maintained that the 

 supposed passages filled up by infiltration w-ere really solid non-tubular portions of the original 



* ' licmarques sur quelques points dc la structure dcs Nummulites,' in '•' Vcrliandl. dcr I'ussi^icli 

 Kaiser, miner. Gesellscb. zu St. Petersburg," 184'7, p. 17. 



