摘要：The xystodesmid milliped tribe Pachydesmini is supported by the autapomorphic absence of bold aposematic pigmentations and possibly also by relative somatic inflexibility; it comprises 3 component genera: PachydesmusCook, 1895; Dicellarius Chamberlin, 1920; and Thrinaxoria Chamberlin and Hoffman, 1950. Three representatives occur west of the Mississippi River—P. clarus (Chamberlin), P. crassicutis crassicutis (Wood), and T. lampra (Chamberlin). New localities are documented in Louisiana and Texas, and literature records are summarized for these states and Arkansas; records of P. clarus from Cherokee County, Texas, are the westernmost in this state for the east-Nearctic xystodesmid fauna. An apparently allopatric population of P. crassicutis crassicutis occurs in Evangeline and Lafayette Parishes, Louisiana. These are the first records of this species from west of the Mississippi River, and new localities of this form are cited from east of the watercourse. Thrinaxoria lampra, known previously in Texas from only Gregg County, is documented from Bowie, Cass, Harrison, Rusk, Sabine, and Titus Counties plus Webster Parish, Louisiana. Diagnoses and pertinent anatomical illustrations are provided for each species including the first cyphopod drawings for P. clarus and T. lampra; occurrences west of the river are depicted on a map. A new tribal diagnosis is published along with a distribution map.
