Malacologia, 1993, 35(2); 261-313
^;^2_ MALACOLOGIA, 1993, 35(2); 261-313 PHYLOGENETIC RELATIONSHIPS AND GENERIC REVIEW OF THE BITTIINAE (PROSOBRANCHIA: GERITHIOIDEA) Richard S. Houbrick Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560, U.S.A. ABSTRACT The anatomy of seven members of the Bittium group is described, clarifying the status of the genus-level taxa comprising it. Bittium reticulatum, the type species of Bittium Gray, is described in depth, thereby establishing criteria for comparisons with other taxa of Bitliinae. The type species of Stylidium Dell and LirobiWum Bartsch, and representatives of Bittiolum Cossmann and Cacozeliana Strand are examined and compared with Bittium, s.s. Results of anatomical studies and a phylogenetic analysis using the Hennig86 and CLADOS programs, with Cehtt)ium as an outgroup, establish monophyly for Bitliinae Cossmann and reveal six different genus-level taxa. A new genus, ittibittium, from the Indo-Pacific, is proposed. Synonymies of each genus- level taxon and representative species examined are presented. Brief accounts of the ecology and zoogeography of each taxon are given. Two taxa formerly attributed to the 6/ff/um-group are herein excluded from it and referred to Cerithium Bruguière. These are Cerithium zebrum Kiener, 1841, and Cerithium boeticum Pease, 1861. The subfamily Bittiinae Cossmann, 1906, is thought to comprise nine genera (four of which were not included in phylogenetic analyses) : Bittium Gray, 1847; Bittiolum Cossmann, 1906; Ittibittium gen. n., Stylidium Dalí, 1907; Lirobit- tium Bartsch, 1911 ; Cacozeliana Strand, 1928; Argyropeza Melvill & Standen, 1901 ; Varicopeza Gründel, 1976; Zebittium Finlay, 1927. The genus Cassiella Gofas, 1987, of uncertain place- ment, is included as a possible member of the group.
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