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Two new genera and five new species of Selachinematidae are described from the New Zealand upper continental slope (350-1240 m depth). Synonchiella rotundicauda sp. nov. is characterised by cephalic setae 0.25 cbd long, mandibles each with two pairs of hooks and two wing-like projections laterally, eight cup-shaped pre-cloacal supplements and short rounded tail. Pseudocheironchus gen. nov. is similar to Cheironchus, but differs from the latter in having a cuticle without lateral differentiation, cephalic setae only slightly longer than the outer labial sensillae, and a posterior buccal cavity with three equal mandibles. Pseudocheironchus ingluviosus gen. et sp. nov. is characterised by mandibles with eight blunt teeth, multispiral amphideal fovea with five turns, and a short rounded tail. Males of this new species with 17-19 cup-shaped pre-cloacal supplements. Males of the genus Cobbionema are described for the first time; C. trigamma sp. nov. is characterised by four long cephalic setae and six smaller outer labial setae in one circle, six rhabdions surrounding the anterior buccal cavity, each with two pairs of pointed projections at their posterior extremities, posterior buccal cavity widening posteriorly, with three pairs of rhabdions fused posteriorly and widening anteriorly, males with two testes pointing anteriorly and with reflexed posterior testis, and no pre-cloacal supplements. Gammanema agglutinans sp. nov. is characterised by a short, stout body often covered in adhering mucus and detritus, cuticle with minute spines, leaf-shaped somatic setae with ducts, sexual dimorphism in the shape of the amphideal fovea (loop-shaped in males and spiral in females), posterior buccal cavity with three pairs of broad, column-shaped rhabdions fused anteriorly, intestine cells with orange-brown granules, and small tubular pre-cloacal supplements. Bendiella gen. nov. is most similar to Halichoanolaimus, but differs from the latter, and all other genera of the family Selachinematidae, in having a cuticle with lateral differentiation consisting of longitudinal rows of larger dots, and from all other genera of the Choniolaiminae in lacking pre-cloacal supplements. Bendiella thalassa gen. et sp. nov. is characterised by amphideal fovea with 5.25 turns, anterior buccal cavity with twelve rhabdions, each with a pair of pointed projections at posterior extremity, posterior buccal cavity with three Y-shaped pairs of slender rhabdions fused from two thirds of distance from anterior ends, and conico-cylindrical tail.
Sipuncula are marine unsegmented worms that can be found in benthic habitats, from shallow to deep-sea waters. In Mexico these worms have been scarcely studied. Among nine studies in the entire Mexican Pacific coasts, seven are from the central and northwestern Mexican Pacific. For over 80 years, only 24 species have been recorded. To improve the knowledge of the sipunculans from the central and northwestern Mexican Pacific, 501 specimens from three scientific collections of Mexico were revised. The specimens were collected by diverse methods from intertidal, subtidal, and bathyal depths (~1000 m), from 27 locations along the central and northwestern Mexican Pacific. Sixteen taxa belonging to nine genera and five families were identified. One species is recorded for the first time in the Mexican Pacific and five new species are described, one from intertidal and shallow subtidal depths: Phascolosoma (Phascolosoma) azteca sp. nov.; two from subtidal depths: Phascolion (Lesenka) salgadoi sp. nov. and Sipunculus (Sipunculus) bastidai sp. nov.; and two from bathyal depths: Apionsoma (Apionsoma) silviae sp. nov. and Apionsoma (Edmondsius) hendrickxi sp. nov.
A new species of echinoderid kinorhynchs, Echinoderes xiphophorus sp. nov. collected from oxidized brown silt at the deepest depression in the Sea of Japan, North-West Pacific, is described and illustrated using light and electron microscopy. This new representative of the most speciose kinorhynch genus is characterized by the unique set of spines and tubes and can easily be distinguished from most of its congeners. The second trunk segment bears three pairs of tubes in subdorsal, midlateral and ventrolateral position in both sexes; one pair of tubes on trunk segment 5 in lateroventral position and on trunk segment 8 in sublateral position; aciculate lateroventral spines on trunk segments 6–9; aciculate middorsal spines on trunk segments 4, 6, 8. This species is well recognized by very long tergal extensions of the posteriormost segment, some of the longest within the family Echinoderidae. Males of Echinoderes xiphophorus sp. nov. are well distinguished from all the congeners by extremely long sword-like appendages dorsally to three pairs of penile spines. The species constitutes the first deep-sea representative of the Echinoderidae in the Sea of Japan and the deepest representative of the Kinorhyncha in this sea.