Figs. 13 to 27. These figures all refer to a very curious group of fossils, termed _Nummulites_, from the supposed resemblance of some of the flat disks to a piece of money. The complexity of their internal structure, and the supposed resemblance of their organization to that of the true Cephalopoda, led to many erroneous opinions as to the nature of the originals. That eminent physiologist, Dr. W. B. Carpenter, has recently investigated the intimate structure of the whole group, and the results are given in a beautiful and masterly memoir in the Quarterly Journal of the Geological Society of London.[57] Dr. Carpenter has clearly shown that these fossils belong to the _Foraminifera_, and not, as some eminent naturalists have supposed, to the _Bryozoa_, or "_Moss-corals_." As the family to which they belong comprises a numerous assemblage of minute organic remains, many of which are delineated in the next plate (Plate LXII.), the reader is referred to the "_Supplementary Notes_," for a general description of the _Foraminifera_, in which is given a restored figure of the supposed living animal of the Nummulite, from Dr. Carpenter's memoir. [Footnote 57: No. 21, for February 1850. "On the Microscopic Structure of Nummulina, Orbitolites and Orbitoides."] Fig. 13. The usual appearance of the common species of Nummulite (_Nummulina lævigata_). From Egypt. Fig. 14. A specimen rubbed down, and exposing the internal cellular structure. Fig. 15. An example in which the outer investment is partly removed. Fig. 16. A vertical section of the same. Fig. 17. This fossil, of which fig. 18, is a vertical section (_Nummulites obtusa_, of Sowerby), appears to belong to a different genus; probably _Orbitolites_, or _Marginopora_. Tertiary strata. Fig. 19. A vertical section of a Nummulite, showing a cavity in the centre, probably from decomposition. Fig. 20. A section of another species of Nummulite (_N. dispansa ?_ of Sowerby);[58] Tertiary strata, India. [Footnote 58: See Sowerby's Mineral Conchology, vol. i.; and Mantell's Fossils of the South Downs.] Figs. 21 to 26, are various sections of a fossil Nummulite, of which fig. 37, represents the flat surface (_Nummulites complanata_, of Parkinson. This fossil belongs to the genus _Discospira_ of Mr. Morris).[59] [Footnote 59: "_Discospira_, Nov. Gen. Disciform, volutions distrial, not embracing the previous ones, cells numerous." _Mr. Morris_, 1850.] Fig. 28. A species of Foraminifera (_Fasciolites_, of Parkinson; _Alveolina elliptica_, of D'Orbigny). Fig. 29. A transverse section. Figs. 30, & 31. Enlarged views of the same fossil. Fig. 31. A longitudinal section.