On Acanthostomum gymnarchi (Dollfus, 1950) with notes on the genera .Acanthostomum Looss, 1899, Atrophecaecum Bhalerao, 1940, Gymnatotrema Morosov, 1955, and Haplocaecum Simha, 1958. - Khalil, L. F. (Journal of Helminthology, 1963)