A new emydine species from the Middle Miocene (Barstovian) of Nebraska, USA with a new generic arrangement for the species of Clemmys sensu McDowell (1964) (Reptilia: Testudines: Emydidae). Zoologische Abhandlungen (Dresden), 51(2), 10 Dezember 2001: 331-353. 335 [Zoological Record Volume 138]