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Juga is a genus of freshwater snails distributed from northern Washington to central California. The taxonomy and classification of the genus has a long and complex history, driven mainly by the features of their highly variable shells. The number of recognized species has fluctuated from ~9 to 11; however, it has been claimed that the actual diversity may be three times that number. We here present a systematic revision using a recently published molecular phylogeny as a framework, which supported the interpretation that there are only nine valid species. Comprehensive review of type material and original descriptions for all available species-group names indicates that almost all species previously considered valid were para- or polyphyletic grades of organization in shell morphology. Most species previously suggested to be putatively new were confirmed to be morphological variants of species already described. Species accounts include complete synonymies and partial chresonymies; the shells and radulae are illustrated and described. Lectotypes are designated for Melania plicifera Lea, 1838, M. silicula Gould, 1847, and M. rudens Reeve, 1860. Three species, Juga caerulea sp. nov., J. canella sp. nov., and J. douglasi sp. nov., are described as new and one species is excluded from the genus. The subgenera Calibasis D.W. Taylor, 1966 and Idabasis D.W. Taylor, 1966 are synonymized with Juga.
Though recent investigations have contributed substantially to our understanding of the Alpine-Dinaric radiation of the genus Zospeum Bourguignat, 1856, its southernmost member, Zospeum troglobalcanicum Absolon, 1916, has remained a taxonomic ghost. The assumed absence of type material, the insufficient original description, and the lack of new samples from its Western Balkan type locality have stymied further clarification. The recent discovery of a single syntype shell housed at the Natural History Museum Vienna now enables the first morphological assessment via 3D X-ray and SEM imaging. Based on this image data, different characters for assessing the southernmost members of the genus are determined and a lectotype is designated. Eleven allied species from 15 Western Balkan populations are described from museum material and recent sampling efforts: Z. amplioscutum Jochum & Ruthensteiner sp. nov., Z. biokovoense Jochum & Ruthensteiner sp. nov., Z. constrictum Jochum & Ruthensteiner sp. nov., Z. dubokidoense Jochum & Ruthensteiner sp. nov., Z. intermedium Jochum & Ruthensteiner sp. nov., Z. kolbae Jochum, Inäbnit, Kneubühler & Ruthensteiner sp. nov., Z. neuberti Jochum & Ruthensteiner sp. nov., Z. njegusiense Jochum & Ruthensteiner sp. nov., Z. njunjicae Jochum, Schilthuizen & Ruthensteiner sp. nov., Z. tortuosum Jochum & Ruthensteiner sp. nov. and Z. tumidum Jochum, Schilthuizen & Ruthensteiner sp. nov. One species, Z. kolbae, is described using DNA sequence data and one species, Z. simplex Inäbnit, Jochum & Neubert, 2021 for which DNA sequence data is already available, is supported by morphological data presented in this study. The DNA sequence dataset (COI, 16S and H3) is included here and implemented in the most recent phylogenetic reconstruction of the genus. A translation of Karel Absolon’s notes from the Balkan scientific expeditions is provided.
The variability of the reticulum pattern, ornamentation and outline of the Urocythereis populations of the La Strea Bay is analysed. The results show that the shell features of the form U. distinguenda (Neviani, 1928) (= U. oblonga Brady, 1866) have to be included within the high variability range of U. margaritifera (G.W. Müller, 1894). Consequently, it is suggested that in the upper infralittoral waters of the inlet two (and not three, as stated in previous investigations) species of the genus Urocythereis presently live. A second form, displaying a relatively low variability, is described as a new species, U. ilariae sp. nov.