Taxonomic notes on the genus Hexanchorus Sharp, 1882 and Heterelmis Sharp, 1882 from Bolivia (Coleoptera, Elmidae)

The genus <i>Hexanchorus</i> Sharp, 1882 is represented in Bolivia by one species, <i>H. tibialis</i> Hinton, 1935. A series of this species was originally collected by Germain in the Yungas of Cochabamba and, in 1935, described by Hinton based on a single specimen that is in poor condition and lacks several key characters. Here, we redescribe <i>H. tibialis</i> based on additional material collected by Germain and describe a new species, <i>H. siriono</i> <b>sp. nov</b>., from Santa Cruz, Bolivia, which exhibits striking male sexual dimorphism in the protarsi. Both species are illustrated with photographs of the habitus and drawings of the male genitalia, and for <i>H. siriono</i> <b>sp. nov</b>. also the female genitalia. Germain's journey in Bolivia and its known elmid fauna are briefly discussed. Additionally, <i>Helmis cervina</i> Grouvelle, 1896 and <i>Helmis longior</i> Grouvelle, 1896, both from Bolivia, are formally transferred to <i>Heterelmis</i> Sharp, 1882. The lectotype of the latter species is designated.