The collection consists of 704 letters addressed to Haldeman, Constantine Rafinesque and Thomas Say, with a letterbook of 22 letters written by Haldeman. In subject, the letters refer to paleontology, conchology, entomology, ichthyology, to Indian relics and to spelling reform. A letter from Leidy is illustrated and several of those written by Haldeman bear pencil sketches. In his letterbook is information about a proposed U. S. Naval Expedition to South America with J. G. Strain, and queries about J. C. Reinhardt as a member of the personnel. The authors number 151. The letters are organized alphabetically by the last name of the writer. A list of correspondence including a synopsis of the contents of each letter is included at the beginning of the collection. Below follows a list of the authors of the letters with the number of letters attributed to them.

Signers of letters and documents: Abbott, C. C. (19) 1875-80; Adair, James (6) 1863-66; Adams, C. B. (21) 1840-49; Agassiz, Alexander, 1859; Allen, J. H. 1845; Anthony, J. G. (37) 1840-53; Auguste (2) 1842-44; Bachi, A. D. 1841; Baird, S. F. (55) 1842-81; Barber, E. A. ( 3 ) 1879; Beadle, E. R. 1867; Benedict, G. W. 1841; Biddle, Cadwalader, 1876; Binney, Amos (2) 1840-41; Binney, W. G. (7) 1860-63; Brakeley, I. H. 1844; Brewer, Thomas, 1856; Brickmore, A. No 1880; Brinckle, W. D. 1851; Browne, P. A. (7) 1849-52; Buchanan, James, 1859;

Calvert, C. M. 1860; Case, William, 1845; Cassin, John, 1842; Charlesworth, Edward (5) 1842-44; Chenu, J. C. 1844; Chevrolat, L. A, A. 1850; Cheney, T, A. 1870; Conrad, To A, 1845; Couper, J. H, (7) 1841-47; Cozzens, Issacher, Jr. (2) 1840-42; "Crooks", George, no d.; Cruchtmanger, L. 1852; Cuvier, Georges, 1830;

Dana, J. D. (24) 1845-67; Dickeson, M. W. (2) 1848; Dimond, Henry, 1845; Dunker, Wilhelm, 1851; Duiatu, I. I. 1842; Emmons, Ebenezer (3) 1846-49; Evans, Erastus (2) 1849; Eschricht, D. F. 1834; Fahnestock, George (3) 1848; Fitch, Asa, 1849; Foreman, Edward, 1843; Frazier, John (14) 1840-49; Frey, S. L. (2) 1879; Galbraith, F. G. (3) 1879; Gallus, 1853; Gambel, William, 1848; Gill, W. L. 1880; Girard, C. F. (5) 1849-55; Goheen, S. M. E. (4) 1840-42; Gory, Jno. 1834; Gould, A. A. (23) 1833-53; Gray, Asa (5) 1849-65; Griffith, R. E. (4) 1843-47; Guex, John A. 1840;

Haldeman, So S. (2) 1849-76; Hall, James, 1845; Hallowell, Edward (7) 1834-49; Hartley, Wm. 1851; Hartmen, W. D. (4) 1848-57; Harris, T. W. (5) 1842-48; Henry, Joseph (13) 1836-76; Hentz, N. M. (5) 1842; Hermot, Henry, 1846; Holbrook, J. E. (4) 1855; Hough, F. B. (7) 1850-69; Howel, Robert, 1857; Jay, J. C. (6) 1842-46; James, T. P. 1855; Jenkins, Thomas (7) 1847-48; Johnson, A. J. 1876; Jones, Eliot (2) 1879; Kirtland, J. P, (2) 1850 & 1853; Lawson, Mahma, 1879; Lea, Isaac (6) 1841-53; LeConte, J. Lo (49) 1844-67; Leidy, Joseph (3) 1847-49; Lesley, Joseph (3) 1858-80; Lewis, G. A. 1869; Lindsley, J. B, 1848; Lynch, W. F. 1847;

McCreath, Andrew, 1879; Markoe, Francis Jr. (3) 1844-46; Meek, F. B. 1866; Mighels, J. W, (12) 1841-43; Melsheimer, F. E. (43) 1842-73; Miller, G. McC. (4) 1854-58; Mochulskii, V. I. (8) 1853-59; Mombeck, J. I. 1869; Morris, J. Go (38) 1842-49; Morris, M. H. 1848; Morris, R. 1849; Newberry, John (2) 1845; Nolan, E. J. (2) 1845; Norton,'Edward (2) 1860; Osten Sacken, C. R. (3) 1857; Packard, A. S. (3) 1867-78; Paine, J. A., Jr. 1866; Parrite, E. (2) 1849; Phillips, J. C. (13) 1842-44; Porter, J. M. 1850; Putman, F. W. (5) 1876-77;

Rathvon, S. S. (3) 1856-79; Rau, Charles, 1879; Reinhardt, J. C. H. (21) 1843-72; Robinson, H. P. 1840; Rogers, H. D. (2) 1848-51; Ruschenberger, W. So W. 1877; Sargent, C. S. (3) 1878; Savage, T. S. (2) 1849-50; Say, Lucy Way (7) 1840-47; Schaum, H. R. (5) 1848-55; Sharswood, William (8) 1858- 70; Silliman, Benjamin ( 6) 1840-51; Shunlarde, B. F. 1848; Shuttleworth, R. J. ( 2) 1843-45; Smith, Sanderson, 1870; Snyder, D. M. 1850; Sommerville, James, 1858; Stabilez, Joseph, 1861; Stansberry, Howard, 1852; Stauffer, Jacob (2) 1855-58; Stimpson, William, 1866; Storer, D. H. 1843; Strain, J. G. (3) 1843-47; Strickland, H. E. 1849;

Tappan, B, 1845; Torrey, John, 1838; Townsend, J. K. (3) 1844; Trego, Charles (8) 1842-72; Troost, Gerard ( 5) 1842-46; Tryon, George Washington, Jr. (12) 1862-80; Tuomey, M, 1845; Tyndall, John, n. do; Uhler, Phillip Reese (2) 1858-65; Van Brunt, Reuben, 1817; Vaux, William, 1850; Vuellerup, C. E. 1850; Ward, Charles (2) 1840; Wagner, Samuel (2) 1856-60; Webster, Noah, 1840; Wetherby, A. G. 1879; Whitaker, Epher, 1855; White, Charles Abiathas, 1878; Whittemore, Thomas Jefferson (4) 1840-41; Wilkes, Charles, 1848; Wright, Samuel, 1843; Ziegler, D. (13) 1842-46.