Bostami Turtle (bostami kasim) a freshwater turtle, Aspideretes nigricans (=Trionyx nigricans), of the family Trionychidae, order Testudines, also known as Black Softshell Turtle, believed to be an endemic species. It is found in a pond at the shrine of Sultan al-Arefin Hazrat bayazid bostami in Chittagong town.The population shows two colours: one with dark brownish-black carapace and the other olive-greenish; the carapace of hatchlings is predominantly light olive-green but marginally darker and having four distinct ocelli on the carapace consisting of five concentric rings.
In adults the carapace length ranges from 39-78 cm with width from 33-71 cm; total wet-body weight may be up to 54 kg; males are generally larger.
In a census made during December 1990, the population was estimated to be about 400. Early reports indicate that the species inhabited a tract intermediate between the Brahmaputra River system and the Arakan system. The nesting season extends from February to May. The mean clutch size is 20 (range 16-24). Incubation period varies from 96-106 days. A critically endangered species, protected by local people for religious reasons, and also by the country's wildlife preservation law. [M Farid Ahsan]