GENUS ORB1TOLITES : HISTORY. 189 



(op. cit.), on the authority of a voyager in the Indian seas, that living Discolites 

 have been found there ; and as there are no existing Nummulites, this statement 

 probably refers to an Orbitolite. LAMARCK, in his second edition, describes, under 

 the title of O. marginalis, a small form of Orbitolite, only 2 millims. ('03 inch) in dia- 

 meter, found upon fuci, corallines, &c. in the European seas ; this he speaks of as 

 the only living example of the genus then known, and he defines it as O. utrinque 

 plana, margins poroso. Besides this species, however, DEFRANCE (loc. cit.) mentions 

 another, more closely resembling the O. complanata of the Paris basin, as existing on 

 the shores of New Holland ; and this seems the first clear indication of the body 

 (afterwards found by MM. QUOY and GAIMARD in that locality, and erected by them 

 into the distinct genus Marginopora}, the structure of which constitutes the chief 

 subject of my present communication. Both these existing forms are described by 

 BLAINVILLE (op. cit.), the first from actual observation, the second on the information 

 of MM. QUOY and GAIMARD, to the manuscript of whose 'Voyage de FAstrolabe' 

 (then unpublished) he refers as his authority. It is singular, however, that after an 

 attentive search through the published "Zoology" of that work, I have not been able 

 to find, either in the text or in the plates, any mention of Marginopora or of Orblto- 

 lites. Of the Orbitolites marginalis, M. DE BLAINVILLE says (op. cit. p. 412), " Nous 

 1'avons etudiee avec soin ; et nous sommes presque convaincu que ces petits corps 

 cre'tace's ne sont pas de veVitables polypiers ; mais bien quelque piece inte"rieure, qui 

 s'accroit par la circonference. II est en effet evident, qu'il n'y a pas de cellules pro- 

 prement dites, a moins qu'on ne veuille regarder comme telles les deux plans de 

 locules qui occupent le bord, et qui n'offrent rien determine*. Tout le reste est cou- 

 vert d'une legere croute cre'tace'e, qui ferme les anciens pores." I think it obvious, 

 from this description, that it was founded on specimens resembling that in Plate VII. 

 fig. 8, in which the marginal row of cells has been laid open above and below by 

 accidental abrasion ; and that the true marginal pores, opening between the protu- 

 berances formed by the cells (Plate V. fig. 1), were overlooked. The genus Margi- 

 nopora, placed by M. DE BLAINVILLE in immediate sequence to Orbitolites, is thus 

 characterized (loc. cit.): " Animaux inconnus, contenus dans les cellules poriformes, 

 excessivement petites, rondes, senses, ^parses dans les sinuosity's, tres fines et tor- 

 tueuses, qui guillochent la circonference d'un polypier calcaire, libre, un peu irre- 

 gulier, disco'ide, concave ou concentriquement strie en dessus comme en dessous, et 

 plus e"pais sur les bords." The two surfaces, M. DE BLAINVILLE further tells us, only 

 exhibit striae of increase, without any trace of pores ; but the turned-up edge is 

 entirely riddled with very fine rounded pores, which are situated in the sinuosities of 

 a very close but shallow engine-turning (guillochis). And when one of its surfaces 

 is rubbed away, the disk is found to be formed of concentric canals, separated by 

 partitions, and themselves divided into cells, thus recalling in some degree the struc- 

 ture of Orbitolites. Having myself had the opportunity of inspecting, by the kind- 

 ness of M. VALENCIENNES, the specimens of Marginopora on which the foregoing 

 MDCCCLVI. 2 c 



