GENUS ORBITOLITES: HISTORY. 191 



simples on multiples; point de spirale." Under this order are ranged the genera 

 CycloUna (D'ORB. 1839), Orbitolites (LAMARCK, 1801, and Marginopora, QUOY et 

 GAIMARD, 1836), Orbitollna (D'ORB. 1847), and Orbltoides (D'ORB. 1847). As I shall 

 have occasion to show that the first three of these genera cannot be separated from 

 each other by any valid distinctions, and that the greater number of the species 

 ranked under them by M. D'ORBIGNY (see his 'Prodrome de Pale"ontologie Strati- 

 graphique') really belong to the same specific type, I must here cite the generic cha- 

 racters which he assigns to them : " CycloUna, Coquille disco'idale, chaque loge 

 perc6e de nombreux pores, faisant un circle entier autour des autres. L'espece con- 

 nue est de 1'etage cenomanien. Orbitolites, Coquille disco'idale, plane, e*gale, et 

 encroutee des deux cote's, pourvue de lignes concentriques. Loges nombreuses, 

 par lignes irre'gulieres, transverses, visibles seulement au pourtour. Nous connais- 

 sons deux especes ; les premieres, de 1'^tage suessonien ; le maximum, dans les 

 mers actuelles. Orbitolina, Ce sont des Orbitolites a cote's ine"gaux ; 1'un, convexe, 

 eucroute, a lignes concentriques ; 1'autre, concave, non encroute', rnontrant des loges 

 nombreuses, par lignes obliques sur le cote", au pourtour. Nous connaissons de ce 

 genre perdu six especes ; les premieres, de l'e"tage albien ; les dernieres, de l'6tage 

 senonien." 



6. The first approach towards a more accurate knowledge of the real nature of the 

 Orbitolite, through an examination of its internal structure, was made (I believe) by 

 myself, in my Memoir " On the Microscopic Structure of Nummulina, Orbitolites, 

 and Orbitoides," read before the Geological Society of London in November 1849, 

 and published in its Quarterly Journal for February 1850. The place assigned to 

 this genus in the system of M. D'ORBIGNY not having been at that time made public, 

 and all other zoologists and palaeontologists having ranked it in close approximation 

 to Lunulites and other Polyparies of the Bryozoic (Polyzoic) kind, I entered upon 

 the examination without the least suspicion that this organism was to be regarded in 

 any other light ; and that Iwas not undeceived in the course of it, may be attributed 

 to the small number of specimens then placed at my disposal for the inquiry by my 

 late friend Professor E. FORBES, and to the circumstance that these specimens were 

 of the type that presents most resemblance to that of a Bryozoic polypary, and were 

 all deficient in the central nucleus, which is the portion most indicative of their 

 Foraminiferous nature. Nevertheless, the marked dissimilarity in structure which I 

 found to exist between the disk of Orbitolite and the polypary of Lunulite or of any 

 other undoubted members of the Bryozoic group, made me even then express myself 

 doubtfully as to its title to be associated with them. In this Memoir, published two 

 years previously to M. D'ORBIGNY'S first announcement of the fact, I showed that the 

 genus Marginopora must be abolished, since its sole representative is so closely allied 

 in structure to the Orbitolite of the Paris basin, that no doubt of their generic iden- 

 tity can be entertained ; the existing M. vertebralis, in fact, being only specifically 

 distinguishable from the fossil O. complanata, by a difference in the form of its super- 



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