MILIOLIDA. 23 



General characters. — Shell a flat, circular disk, composed of one or more layers 

 of concentric zones arranged around a central or primordial portion. Each zone or 

 chamber subdivided by depressions in the shell wall (marked externally by surface 

 fmTows) into ovate or rectangular chambers, whose long diameter is in the direction of 

 radii. Pseudopodial orifices situated in depressions on the lateral face of the peripheral 

 chamber. Texture porcellanous, diaphanous. 



1. Orbitolites orbicultjs, Forskdl. Plate III, figs. 45 — 47. 



Umbilicus mariiius, Planeus, 1744. Fab. Columnse Lyuc. Phytobas. Addit. p. 136, pi. 38, 



fig. p. 

 Helicite et Opercule, Guettard, 1770. Mem., vol. iii, p. 434, pi. 13, figs. 30—32. 

 Nautilus okbiculus, Forskdl, 1775. Descrip. Anim., p. 125, No. 66. 

 Orbitolites complanata, Lamarck, 1801. Syst. Anim. s. Vert., p. 376. 

 DiscoLiTHUs X., Fortis, 1802. Mem. Hist. Nat., vol. ii, p. Ill, pi. 3, figs. 4, 5. 

 Madreporite, Deluc, 1803. Journ. Phys., vol. Ivi, p. 349, fig. 9. 

 DiscoLiTES coNCENTRicus, Monffort, 1808. Coiichyl. System., vol. i, p. 186. 

 Orbitolites plana, Brotigniart and Cuvier, 1808. Ossem. Foss., vol. ii, part 2, p. 270. 

 Orbulites marginalis, 0. complanata, Lamarck, 1816. Anim. s. Vert., vol. ii, p. 196, 



Nos. 1, 2. 

 Orbitolites complanata, Schiveiyger, 1819. Beobacbt., pi. 6, fig. 60. 

 Orbulites planulatus, Blainville, 1825. Diet. Sc. Nat., xxxvi, p. 294; Atlas Zoopb., 

 pi. 47, fig. 2; Actinologie, p. 441, pi. 72, fig. 2. 



— MARGINALIS, 0. COMPLANATA, Lamoiiroiix, 1821. Gen. Polyp., pp. 44, 45, 



pi. 73, figs. 13—16. 

 Orbitolites complanata, Defranee, 1825. Diet. Sc. Nat., xxxvi, p. 294. 



— — 5/-0M, 1825. Syst. Urwelt. Pflanz., pi. 6, fig. 18; 1838, Letb. 



Geogn. pi. 35, fig. 22. 

 Sorites orbiculus, Ehrenberg, 1838. Berlin Trans. (1839), p. 112, pi. 3, fig. 2. 

 Ampiiisorus Hemprichii, Ehrenberg, 1838. lb., p. 114, pi. 3, fig. 3. 

 Orbitolites complanata, 0. elliptica, Michelin, 1840 — 45. Icon. Zooph., p. 167, pi. 46, 

 • • fig. 4, and p. 277, pi. 61, fig. 11. 



— — Carpenter, 1850. Quart. Journ. Geol. Soc, vol. vi, p. 30, pi. 6, 



fig. 23 ; pi. 7, figs. 24—30. 

 Orbiculina (ORBiroLiTEs) complanata, Williamson, 1851. Trans. Micr. Soc, vol. iii, 



p. 115, pi. 17, fig. 8 ; pi. 18, figs. 9—14. 

 Orbitolites complanatus, Jones, 1854. Morris's Cat. Brit. Foss., 2nd edit., p. 39. 



— complanata, Carpenter, 1856. Pbil. Trans., vol. cxlvi, p. 181, pis. 4 — 9; 



1862, Introd. Foram., p. 105, pi. 9. 



— — ParAwand /owes, 1860. Ann. N. H., 3rd ser., vol. v,p. 291, &c. 



Characters. — Shell circular, discoidal, flat, sometimes slightly bi-concave. Chambers 

 consisting of narrow concentric bands, subdivided into chamberlets, which alternate, after 

 the pattern of the Spiral of Archimedes (Haughton) ; surface marked by furrows, inchcating 

 the margins of the chamberlets. Shell composed of one (simple type) or several (complex 



