On the anatomy and systematics of Juga from western North America (Gastropoda: Cerithioidea: Pleuroceridae)

The family Pleuroceridae is a speciose and ecologically important family of limnic gastropods in North America and eastern Asia. ]uga is the only native pleurocerid genus that occurs in Pacific drainage systems of Western North America, but has only recently been accepted as independent from other North American genera and may have affinities to Asian pleurocerids. As such, this genus represents a key piece to the puzzle of pleurocerid systematics. Howe\'er, published accounts oi Juga anatomy are limited to the reproductive system. Consequently, the anatomy of three species is described herein; these three taxa represent the type species of the three extant subgenera: Juga ijuga), J. (Calibasis), and J. (Oreobasis). A lectotype is designated for Goniobasis acutifilosa Stearns, 1890, the type species of Calibasis; Melania newberryi, the type species of Oreobasis, is here removed from the synonymy oijuga bulbosa. This analysis confirms that Juga shares many anatomical features with other North American and Asian pleurocerids, but is clearly set apart from eastern North American pleurocerids in features of the ovipositor pore, radula, midgut, kidney, and pallial gonoduct. Juga is distinct from all other limnic cerithioideans known thus far in the form of the midgut crescentic ridge, the configuration of prostate glands, and an evagination of the kidney wall separating the main chamber and bladder. Based on information currently available, unlike molecular data, there is no morphological feature unambiguously linking Juga to Asian pleurocerids. Anatomically, Oreobasis is strikingly similar to Juga sensu stricto and is synonymized wdth it, whereas Calibasis is retained as a \'alid taxon.