DESCRIPTION OF GENUS AND SPECIES. 



Orhitolites, Lamarck. 



Orbitoh'tes, Lamarck, Systfeme des Animaux sans Vert&bres (1801). 



Orhuliteg, Lamarck, Histoire Naturelle des Animaux sans Vertebres [1816-22]. 



OrhitolHes, Milne-Edwards, in posthumous edition of Lamarck's Animaux sans Vertebres. 



Marginopora, Quoy and Gairaard, in De Blainville's Manuel de I'Actinologie, p. 412 [1834]. 



Oi-hitolites, d'Orbigny, Cours Elementaire de Pal^ontologie [1849J. 



OrbicuUna, Williamson, Traus. Micr. Soc, vol. iii. [18-52]. 



The fundamental distinction of this Generic type, which separates it from all other 

 " porcellanous "-shelled Foraminifera (the existing genus Cydodypeus, Carpenter, and the 

 fossil genus OrUtoides, d'Orbigny, representing it in the " vitreous " series), consists in its 

 cydical plan of growth, that is, in the arrangement of the sub-segments of the sarcodic 

 body of the animal, connected together by annular " stolons," in concentric zones ; 



Fig. 1. — Cyclical arrangement of parts of sarcodic Body of OrbitolUes 



a. Primordial segment. 



*, Circumaraliient segment ; each subsequent formation divided into sub-segments connected by annular stolons, 

 and each annulus connected with the ue.\t by radial stolon-processes. 



a new annulus being formed by the extension of radial sarcodic "stolon-processes" 

 from the last or outermost of the preceding annuli, giving origin to a new circlet 

 of sarcodic masses, which put forth lateral extensions that unite them with their 

 fellows, and thus complete the ring (fig. 1). The innermost of these sarcodic rings 



