Abstract. We extend Stanley’s work on alternating permutations with extremal number of fixed points in two directions: first, alternating permutations are replaced by permutations with a prescribed descent set; second, instead of simply counting permutations we study their generating polynomials by number of excedances. Several techniques are used: Désarménien’s desarrangement combinatorics, Ge...

the systematics, morphology, distribution, biology, economic importance and conservation of the spiny eel ( mastacembelus mastacembelus ) of iran are described, the species is illustrated, and a bibliography on this fish is provided. the single species is distributed in southern iranian basins, including karkheh, karun, jarrahi and helleh river basins, mostly part of the tigris river and persia...

Susamyia Ziegler & Gilasian gen. nov. and its type species mira et sp. are described from southwestern Karkheh National Park southeastern Jazmourian Wetland of Iran. Drawings terminalia head the male as well images habitus, egg provided. is incorporated into identification key to Palearctic tachinid genera Tschorsnig Richter (1998). The systematic position in tribe Goniini (Exoristinae) dis...

This paper provides information on the geographic distributions of two cyprinid species: Hemiculter leucisculus (Basilewsky, 1855) and Alburnus caeruleus Heckel, 1843, in the world and the entire drainage systems in Iran. The new distribution records were taken from Maroon River (Jarrahi River system) and Chardaval River (Karkheh river system), both in Tigris River basin showing wide and narrow...