S U P P I- E M E N T. 705 



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Free; disk-shape, circular, nearly flat above and below; both sur- 

 faces minutely porulose. 



This genus was established by Lamarck, and originally named 

 Orbitolites. It contains, beside some fossils, a single recent Mediter- 

 ranean species (O. marginalis], which is about a line in diameter. 

 Blainville doubts its being a zoophyte, arid suggests that it may be an 

 internal piece from some animal. He adds that it has no proper cells, 

 and enlarges by growth at the margin. 



Lamarck, ii. 302. Blainville, Man. d'Actinologie, 411. 



GENUS MARGINOPORA. QUOY & GAYMARD. 



Liberce; orbiculate disciformes. Cor alia supra infraque planiuscula et 

 concentrice striatula ; margine subtiliter punctata ; interne cellulosa. 



Free; very thin disk-shape, circular. Coralla nearly plane above and 

 below, and concentrically faint striate; margin minutely punctate; 

 internal texture concentrically cellular. 



These small disks are found unattached, and are of common occur- 

 rence about the reefs of the Pacific. The punctations of the margin 

 (pi. 60, fig. 9 a) do not appear to be punctures, except in worn speci- 

 mens, and the remark of Blainville with regard to the nature of the Or- 

 bulites, applies here with equal force. The pores of the interior, which 

 appear as shown in figure 9 b, pi. 60, on polishing down the surface, are 

 not enclosed cellules, as in species of Bryozoa. We distinguish, under 

 a magnifier, concentric "calcareous lines, about a tenth of a line apart, 

 which are connected by minute points or columns, in several ranges, 

 above one another; and the cellules are merely the intervals thus left. 

 A cross section in the line of a radius, shows nearly the same struc- 

 ture as a horizontal section. It is, therefore, altogether probable that 

 each disk belongs to a single animal, and is an internal formation, in- 

 creasing, as in the Orbulites, by the margin. 



This genus was established by Quoy and Gaymard, and named in 

 allusion to the character of the margin. They report to it a single 



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