Morphology of some fossil lacustrine centric species from the western United States assigned to the genus Cyclotella (Bacillariophyta), including four described as new Author Kociolek, J. P. University of Colorado Museum of Natural History and Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado, 80309, USA Author Khursevich, G. K. Department of Botany, M. Tank Belarus State Pedagogical University, 18 Sovetskaya Street, 220809 Minsk, Republic of Belarus E? mail: galinakhurs. 41 @ mail. ru text Phytotaxa 2013 2013-08-29 127 1 81 99 http://dx.doi.org/10.11646/phytotaxa.127.1.11 journal article 10.11646/phytotaxa.127.1.11 1179-3163 5085519 Cyclotella kansasica Hanna (1932: 376) ( Figs 10–24 ) Hanna 1932 . University of Kansas Science Bulletin 20: 376, pl. 31, fig. 6. Material examined: — USA . Kansas : Wallace County, Diatom marl from center Sec. 11, T .11S., R 38W, Marshall ranch, North Fork Smoky Hill River, Ogallala Formation. CAS Accession Number 2383 ( CAS !). This is the type material studied by Hanna (1932) . USA . Kansas : Wallace County, Sec. 12, T .11S., R 38W. CAS Accession Number 604437, Slide numbers 423092, 423093 ( CAS !). Description: —Valves are circular, nearly flat, 4.5–16.5 µm in diameter, with several girdle bands and a well-defined border between the central area and the marginal alveolate zone. Central area with one more or less well-developed depression at the center and a variable number of areolae which are arranged irregularly or in short radial rows. Marginal zone extending a little over 1/3 of the valve radius consists of alveolate striae fascicles, 8–12 in 10 µm , separated by hyaline interfascicles. Striae fascicles are of equal length. They contain 3–4 rows of puncta, 40–60 in 10 µm . Alveoli are simple. Length of alveolar openings is almost equal to the length of striae fascicles. Marginal fultoportulae with 3 satellite pores are located on every costa or every second costa separating alveolar openings internally. A single rimoportula occurs at the marginal ends of one of the costae. Spines are present at the junction of the valve face and mantle at every interfascicle, but they may be broken.