New species of Rhynchelmis (Clitellata, Lumbriculidae), with observations on the Nearctic species

The Nearctic species of Rhynchelmis (Lumbriculidae) are distinguished from the Palearctic group Rhynchelmis s. str. by longitudinal muscle bands that do not curl inwards. Six new species from western North America support the existence of two major groupings within the Nearctic fauna. Species in Gro up 1 are distinguished from other Rhynchelmis by large penial bulbs and mul tiple spermathecal diverticula. Within Group 1, Rhynchelmis yakimorum n. sp ., Rhynchelmis monsserratus n. sp., Rhynchelmis gustafsoni n. sp. and Rhync helmis utahensis n. sp. differ from the related Rhynchelmis (=Sutroa) rostr ata in having shea penes and spermathecae with 2 short, lobed diverticula. R. monsseratus is distinguished by a single, median spermatheca, R. gustafs oni has closely appressed, median spermathecae and atria, and R. utahensis differs in structural details of spermathecae and male pores. Rhynchelmis g ilensis n. sp. has a single, median spermatheca with unbranched diverticula and distinctive nephridia. Redescription of material from the type localit ies of both Sutroa alpestris and R. rostrata supports their combination. Gr oup 2, corresponding in part to Rhynchelmoides, is distinguished from Group 1 mostly by characters that are inconsistent or appear plesiomorphic. With in Group 2, Rhynchelmis saxosa n. sp. closely resembles Rhynchelmis alaskan a, except for the absence of lateral blood vessels in posterior segments an d distribution of prostates. Rhynchelmis elrodi and Rhynchelmis glandula co nsistently differ in presence of ventral glands and have different distribu tions, so their supposed synonymy is rejected.