''Rhynchelmis'' is the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of 30 species of aquatic

oligochaete Oligochaeta () is a subclass of animals in the phylum Annelida, which is made up of many types of aquatic and terrestrial worms, including all of the various earthworms. Specifically, oligochaetes comprise the terrestrial megadrile earthworms ...

s from the Northern Hemisphere, with 11 species from

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

and 19 from

Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelago a ...

. They are part of the family

Lumbriculidae The Lumbriculidae are a family of microdrile oligochaetes common in freshwater environments, including streams, lakes, marshes, wells and groundwater. They should not be confused with the earthworm family Lumbricidae. Many species and genera are ...

, which are among the largest of the microdriles. They are generally defined as having atria in segment X and

spermatheca The spermatheca (pronounced plural: spermathecae ), also called receptaculum seminis (plural: receptacula seminis), is an organ of the female reproductive tract in insects, e.g. ants, bees, some molluscs, oligochaeta worms and certain other ...

e in segment VIII (Fend & Brinkhurst, 2000). The

prostomium The prostomium (From Ancient Greek, meaning "before the mouth"; plural: prostomia; sometimes also called the "acron") is the cephalized first body segment in an annelid worm's body at the anterior end. It is in front of (but does not include) th ...

generally has a

proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elong ...

, from which the genus has got its name. ''Rhynchelmis'' contains several subgenera, all of which have previously held genus rank: ''Rhynchelmoides'' with four species, ''Sutroa'' with six species, and ''Pseudorhynchelmis'' with nine species. Further, four species - '' Rh. aleutensis'', '' Rh. brooksi'', '' Rh. malevici'' and '' Rh. orientalis'' - cannot positively be placed in any of the subgenera.

References

* Fend, S. V. & Brinkhurst, R. O. (2000): New species of ''Rhynchelmis'' (Clitellata, Lumbriculidae), with observations on the Nearctic species. ''Hydrobiologia'' 428: 1-59. Lumbriculidae Annelid genera {{annelid-stub