In the phylogenetic reconstruction, based on the mitochondrial cytochrome c oxidase subunit I (COI) gene, the Adriatic taxon results clearly indicate that this is distinct from the other species of the genus and formed a well-supported clade with other Streblospio sp. specimens from India. Nucleotide divergences calculated between the Adriatic specimens and the other Streblospio species are higher than the intraspecific range reported for the genus and support the description of a new species. Morphological characters important for differentiation of the new species herein described from congeneric species are discussed and an updated key for Streblospio species is provided.Four specimens of the sea cucumber Ypsilocucumis californiae Massin Hendrickx, 2011 were obtained during sampling operations off western Mexico. These specimens permit identification of this species as a member of the deep-water holothuroid community off the west coast of the Baja California Peninsula. Previous records correspond to four locations (including the type locality) in the Gulf of California, where eight specimens were collected. SEM ossicles images are provided for the first time and new ecological data associated with the presence of this species are available temperature, 5.34‒8.38 °C; dissolved oxygen, 0.15‒0.28 ml O2/l and salinity, 34.42‒34.51 ups. The specimens were present in a wide variety of sediments with an organic carbon content of 3.18‒5.20 mg C/g (5.47‒8.95 % organic matter). Density values indicated low abundance of this species in the area (2.63‒3.94 orgs/ha). Records presented here were in a depth range from 540 to 776 m, which corresponds to the lower limit of the Oxygen Minimum Zone of the eastern Pacific. Additional records are provided for the West Atlantic Ypsilocucumis asperrima (Théel, 1886) and a key to the species of Ypsilocucumis is provided.Two species of Philothalpus Kraatz are described as new P. anapodos n. sp. Chatzimanolis, from Madre de Dios, Peru and P. boreios n. sp. Chatzimanolis from El Salvador, Guatemala and Costa Rica. Additional distributional records are provided for P. asymmetros Chatzimanolis Ashe, P. bilobus Chatzimanolis Ashe, P. fervidus (Erichson), P. juanecoi Asenjo Ribeiro-Costa, P. mundus (Sharp) and P. rugosus Chatzimanolis Ashe. A revised identification key is provided that includes all species of Philothalpus.A new species of the genus Pratylenchoides has been described. It was found in Polish Jurassic Highland, in Ojców National Park. Pratylenchoides ojcowensis sp. nov. was isolated from the soil located around tangled roots of Elymus sp. and Trifolium sp. This species is marked by a conical head in both females and males which is not separated from the body contour and has with 4-5 annuli; a relatively short stylet (20.3-21.3 µm females, 17.7-20.9 µm males) with oval knobs directed posteriorly; the dorsal pharyngeal nucleus located anterior to the cardia (the subventral pharyngeal nuclei located posterior; a pharyngeal lobe of length about two body widths (1.8-2.6); a lateral field with 6 lines in the middle part of body and sometimes with partially areolated outer bands; intestinal fasciculi present; round sperm in the spermatheca in females; a female tail with a maximum of 29 annuli, and an annulated tail terminus. The status of the new species has been verifiied by DNA sequencing and phylogenetic analysis of the 28S rDNA region. The results obtained in the study indicated that P. ojcowensis sp. nov. is most related to P. alkani, P. ritteri and P. nevadensis from which is distinguished by the shape of the female head (conoid vs rounded), shorter stylet in females (20.3-21.3 µm vs 22.0-25.0 µm, 21.0-25.0 µm, 22.0-26.0 µm) and differences in 28S rDNA sequences. In addition (as per the original descriptions Yüksel 1977, Sher 1970, Talavera Tobar 1996) it is distinguished from P. alkani by smaller number of male's head annuli (4-5 vs 7-9), from P. ritteri it is distinguished by posteriorly directed stylet knobs (vs directed laterally), from P. nevadensis it is distinguished by oval and posteriorly directed stylet knobs (vs rounded and directed laterally).Bunocephalus hertzi, new species, is described from two tributaries of the upper Rio Paraná basin. Because the type series of B. larai (the only other species of Bunocephalus in the basin) is lost, a redescription of B. larai is also provided herein. Bunocephalus larai and B. hertzi can be distinguished from all its congeners, except B. minerim, by the absence of an epiphyseal bar (vs. present). From B. minerim, both species can be distinguished by the presence of 10 principal caudal-fin rays (vs. 9). Bunocephalus hertzi can be differentiated from B. larai by the longer coracoid process size (11.9-16.2% vs. 6.7-9.8% SL), shorter maxillary barbel (just reaching the pectoral fin origin; 54.6-67.4% vs. 73.7-84.6% HL) and skull ornamentation represented by five bony protuberances between the posterior end of the occipital and the origin of the dorsal fin (vs. P7C3 datasheet four bony protuberances).Limonius sapphirus sp. n. and L. onyx sp. n. are described from Taiwan, representing the first record of the genus Limonius in Taiwan. We provide an updated key to the genera of the subtribe Athouina in Taiwan and general morphological information of L. eximius Lewis, 1894 and L. ignicollis Lewis, 1894, which are endemic to Japan, for comparison with the two Taiwanese species. We believe that the two Taiwanese species and L. ignicollis are closely allied, sharing morphological characteristics of the lateral carina of prothorax, prosternal spine and aedeagus.Based on a census of the polychaete fauna of the Socotra Archipelago in the Indian Ocean we report here new findings on the genus Syllis Savigny in Lamarck, 1818. These ten species are newly recorded from this area Syllis alternata Moore, 1908; Syllis bouvieri Gravier, 1900; Syllis broomensis (Hartmann-Schröder, 1979); Syllis compacta Gravier, 1900; Syllis crassicirrata (Treadwell, 1925); Syllis gerlachi (Hartmann-Schröder, 1960); Syllis hyalina Grube, 1863; Syllis lutea (Hartmann-Schröder, 1960); Syllis schulzi (Hartmann-Schröder, 1960); Syllis ypsiloides Aguado, San Martín Ten Hove, 2008. Additionally, Syllis qamhiyn sp. nov. is described as a new species, characterized by its conspicuously thick and short dorsal cirri filled with a gelatinous substance and reduced number of compound chaetae from medium to posterior parapodia, with enlarged shafts and short blades which become almost unidentate and do not fuse with shafts. Following an examination of the holotype of S. bouvieri, its status as a valid species and not as synonym of Syllis prolifera Krohn, 1852, as considered by some authors (see Licher 1999) is confirmed, and a redescription is included.