extremely so. At least six different polyvalent antivenoms are available. Five are produced by Aventis Pasteur (France), Pasteur Merieux (France) and SAIMR (South Africa). All of these specifically protect against B. arietans and four also cover B. gabonica. At least one protects specifically against bites from B. nasicornis: India Antiserum Africa Polyvalent. In the past, such antivenoms have been used to treat bites from other Bitis species, but with mixed results. Species *) Not including the nominate subspecies. T) Type species. Taxonomy Other species may be encountered in literature, such as: B. albanica – Hewitt, 1937 B. armata – Smith, 1826 Lenk et al. (1999) used molecular data (immunological distances and mitochondrial DNA sequences) to estimate the phylogenetic relationships among species of Bitis. They identified four major monophyletic groups for which they created four subgenera: Bitis – B. arietans Calechidna – B. albanica, B. armata, B. atropos, B. caudalis, B. cornuta, B. heraldica, B. inorata, B. peringueyi, B. rubida, B. schneideri, B. xeropaga Macrocerastes – B. gabonica, B. nasicornis, B. parviocula Keniabitis – B. worthingtoniFor now, this division is of little consequence as far as the nomenclature is concerned. However, the definition of subgenera within a genus is often the sign of an impending split. Therefore, those interested in these snakes would do well to familiarize themselves with these new subgenera. References Further reading Duméril A-M-C, Bibron G. 1844. Erpetologie Générale ou Histoire Naturelle Complete des Reptiles. Vol.6. Paris: Librarie Encyclopédique de Roret. 609 pp. [60]. Gray JE. 1842. Monographic Synopsis of the Vipers, or the Family Viperidæ. Zoological Miscellany, London 2: 68–71. [69]. Laurenti J.N. 1768. Specimen medicum, exhibens synopsin reptilium emendatum cum experimentis circa venena et antidota reptilium Austriacorum. Vienna: J.T. de Trattern. 214 pp. [103]. Merrem B. 1820. Versuch eines Systems der Amphibien. Tentamen systematis amphibiorum. Marburg: J.C. Krieger. xv + 191 pp. [150], 1 pl. Reuss T. 1939. "Berichtigungen und Ergänzungen zu meinen Arbeiten über Toxicophidier, 1938." Zeitschrift für Aquarien- und Terrarien-Vereine, Berlin (1), 13–14 [14]. U.S. Navy. 1991. Poisonous Snakes of the World''. New York: Dover Books. (Reprint of US Govt. Printing Office, Washington D.C.) 232 pp. . External links Southern adder (Bitis armata) at ARKive. Accessed 5 October 2006. Snake genera Taxa named by John Edward Gray