OF NORTH AMERICA.. 501 



1901, a. The Loess of Iowa City and Vicinity. Bull. Lab. Nat. Hist., Univ. 



Iowa, V, p. 195. 

 1901, b. Report of Professor B. Shimek on the Loess Mollusks in Geology 



of Pottawattamie County, by J. A. Udden. Iowa Geol. Surv., XI, pp. 



261-266. 

 1901, c. The Loess of Iowa City and Vicinity. Amer. Geol., XXVIII, p. 344. 



1903. Report of Professor B. Shimek on the Fossils from the Loess of Mills 

 and Fremont Counties. In Geology of Mills and Fremont Counties, 

 by J. A. Udden. Iowa Geol. Surv., XIII, pp. 170-175. 



1904. Evidences (?) of Water-deposition of Loess. Bull. Lab. Nat. Hist., 

 Univ. Iowa, V, No. 4, pp. 369-381. 



Shiverick, C. E. 



1840? See Taylor, W. K. 

 Shuttleworth, R. J. 



1854. Beitrage Zur naheren Kenntniss der Land-und Siisswasser-Mollusken 

 der Insel Portorico. Mittheilungen der Natur. Gesel. Bern, 1854. 



Siebenthal, C. S. 



1909. See Darton, N. H. 

 Siebold, C. Th. von. 



1875. Ueber das Anpassungs-Vermogen der mit Lungen athmenden Siiss- 

 wasser-Molluscen. Sitzungs. der Math. Phys. Classe der K. B. Acad. 

 der Wiss. zu Munchen. Band VI, heft 1, p. 39. 

 Simpson, C. T. 



1886. Contributions to the Mollusca of Florida. Proc. Daven. Acad. Sci., 

 V, pp. 45-72. 



1887. On the Distribution of Land and Fresh-water Shells of the Tropics. 

 Conch. Exch., II, pp. 37, 50. 



1888. Notes on Some Indian Territory Land and Fresh-water Shells. Proc. 

 Nat. Mus., XI, pp. 449-454. 



1889. What is a Species? Nautilus, III, pp. 88-90. December. 



1894. Distribution of Land and Fresh-water Mollusks of the West Indian 

 Region, and their Evidence with Regard to Past Changes of Land 

 and Sea. Proc. U. S. Nat. Mus., XVIII, pp. 423-450. 



1895. The Classification and Geographic Distribution of the Pearly Fresh- 

 water Mussels. Proc. U. S. Nat. Mus., XVIII, pp. 295-343. 



1900. Synopsis of the Naiades or Pearly Fresh- Water Mussels. Proc. U. S. 

 Nat. Mus., XXII, pp. 501-1044. 



Singley, J. A. 



1893, a. List of Pleistocene and Recent Shells. Geol. Surv. Texas, Fourth 



An. Rep. for 1892, pp. 186-190. 

 1893, b. Contributions to the Natural History of Texas. Part I, Texas 



Mollusca. An. Rep. Geol. Surv. Texas, IV, pp. 297-343. 

 Small, H. B., and Symes, P. B. 



1882. Report of Conchological Branch. Trans. Ottawa Field Nat. Club, I, 



p. 57. 

 Smith, Maxwell. 



1906. Shells of Richfield Springs, New York, and Vicinity. Nautilus, XX, 

 pp. 89-91. December. 



