During a survey of the marine Crustacea of the Cayman Islands, Heteromysis ebanksae, new species was discovered in depths of 1–3 m adjacent to Little Cayman Island and from North Sound, Grand Cayman Island. The new species, which belongs to the subgenus Olivemysis Băcescu, 1968, collected from live bottom and sea grass habitats, is distinguished from other closely related species in the western Atlantic by differences in the setation of thoracic endopod 3, male pleopod 4 and the telson. Heteromysis ebanksae has 2–9 flagellated spiniform setae on male pleopod 4, 6–10 spinules along the anterior half of the telsonic cleft, and each apical lobe of the telson has a pair of spiniform setae, the outer 1.2 times longer than the inner. A diagnostic table separating the new species from H. actinae Clarke, 1955, H. bermudensis G. O. Sars, 1885 and H. floridensis Brattegard, 1969 is presented.

Eighteen species of sergestid shrimps are reported from 72 benthic trawl, towed net, dip net, and seine collections made by R/V Albatross in the Philippines in 1907–1910. Included are one species each of Acetes, Allosergestes, Deosergestes, Neosergestes, Parasergestes, Sergestes, and Sicyonella and eleven species of Sergia. Sergia foresti, taken from off Mindanao, Philippines, is described as new.

The syntypes of the Russian freshwater crayfish, Cambaroides schrenckii (Kessler, 1874) and Cambaroides sachalinensis (Birstein & Winogradow, 1934), that were considered lost, were recently found at the Zoological Institute of the Russian Academy of Sciences, St. Petersburg. Our re-examination has shown that C. sachalinensis is a junior synonym of C. schrenckii. A lectotype of C. schrenckii is designated, and a description is made on the basis of type material and supplemental material recently collected from the Russian Federation. Detailed information on geographic distribution of this species is provided. Morphology and behavior of juveniles, and the position of spermatophores attached to the adult females also are recorded. The phylogenetic position of this genus is evaluated based on these characteristics.

Three new species of Pseudotaeniacanthus Yamaguti & Yamasu, 1959 were discovered infesting gill filaments of the laced moray, Gymnothorax favagineus Bloch & Schneider, caught off southern Taiwan. Two of these species, P. dentiferus, new species and P. similis, new species, are distinguished from their congeners by the presence of a tooth-like projection on the ventral side of the proximal segment of their antennule. Pseudotaeniacanthus similis differs from P. dentiferus in having a plumose seta (instead of a spine) on the outer margin of the terminal, endopodal segments of legs 2–4. The third species, P. conspicuus, new species, is distinguished by the presence of a rostral bar partially visible in dorsal view and a small protuberance on the posterolateral margin of the cephalothorax. A key to the 11 species of Pseudotaeniacanthus is provided.

The lateral face of the cephalosome deepens progressively during the six stages of copepodid development of Tegastes falcatus. A simple aesthetasc on the second from the proximal segment of the antennule is transformed into a bifurcate aesthetasc during the molt to copepodid II. Copepodids II–VI bear eight setae on the caudal ramus, a number unique to copepods. Formation of the arthrodial membrane separating the middle segment and distal complex of the endopod of swimming legs 2–4 is delayed until CVI, one stage later than the exopod. Gender dimorphism initially is observed in antennular segmentation, setation of the maxilliped and rami present on leg 5 at copepodid IV. At copepodid V, males and females differ in antennular segmentation, rami present on leg 5 and the shape of leg 6. Gender dimorphism at copepodid VI also includes the shape of the cephalosome, of the genital triple-somite complex, and of one seta on the caudal ramus.

The morphology of the ventral attenuation of the sixth and seventh thoracic somites, the anterior abdominal somite, and the degree of rotation of leg 6 are compared for males of Tegastes falcatus, T. gemmeus, T. ctenidus, Parategastes conexus and Syngastes sp. Tegastes is composed of species whose females and males have a genital triple-somite (sixth and seventh thoracic somites plus the anterior abdominal somite not separated by arthrodial membranes). Tegastidae are diagnosed as species with the rami of leg 1 unsegmented and basis elongate; male genital somite (seventh thoracic) extended ventrally; male leg 6 present only on one side; protopod of male leg 6 unarmed; female embryo sac with 3–4 embryos; female leg 5 with broad baseoendopod forming embryo sac chamber. Species of the lineage Tegastidae plus Peltidiidae have males with an asymmetrical leg 6 in addition to the rectangular distal basal endite of the maxillule noted by Seifried (2003). A stout ventral spine with hyaline membrane on the distal segment complex of the exopod of swimming leg 4 also may be a synapomorphy for this lineage.

The adult male of Cypridinodes plax Kornicker, 1991 collected on the Dana Expedition of 1928 in Apia Harbor, Samoa, is described and illustrated. Two male specimens from the same station that had been previously referred to Cypridinodes asymmetrica (Müller, 1906) by Poulsen (1962) were examined and found to be Cypridinodes plax Kornicker, 1991.

Eight species of myodocopid Ostracoda (six Myodocopina, one Halocypridina, and one Cladocopina) are reported from 30 to 60 m depths in Moss Town Blue Hole, an ocean blue hole located in a bay on the west side of Great Exuma Island, Exuma Cays, Great Bahama Bank. The collection from Moss Town Blue Hole contained no new species, but five species had not been reported previously from the blue holes of Great Exuma Island, and three species had not been reported previously from the blue holes of the Exuma Cays. The collection provided the opportunity to describe the adult male and female, as well as early instars, of Eusarsiella fax and Metapolycope duplex, and the adult female of Eusarsiella merx, and also, to compare the ostracode populations in the various niches in the Exumas.

Pentametrocrinus paucispinulus, new species, is described from a specimen collected on Pioneer Seamount off California in 1768 m. Like its closest congeners, it bears the first pinnule on the second brachial, but it differs in several characters. For example, P. varians and P. australis have longer tapered cirri with more segments, and P. spinosus has multiple rows of thorny stumps on the proximal arms. This is the first record of the genus from the eastern Pacific Ocean. A key to the species in the genus Pentametrocrinus is included.

We describe a new species, Mastigoteuthis microlucens, of the family Mastigoteuthidae from the tropical North Pacific. Its most distinctive morphological character is the presence of microscopic photophores in the integument. Morphological data indicate that its closest relative is the Atlantic Ocean species Mastigoteuthis magna. Molecular data from three genes, based on four species for which molecular data is available, indicates that Mastigoteuthis microlucens differs from its closest relative, M. magna, by a sufficient degree to substantiate its separate species status.

Fridericia dianchiensis, a new enchytraeid species collected from Yunnan Province, is described here. It is characterized by a combination of the following characters: 1) lateral bundles containing maximum 3 chaetae; 2) esophageal appendages with 3–4 simple, terminal branches; 3) dorsal vessel originating in XX–XXIII; 4) subneural glands absent; 5) seminal vesicle large, occupying two segments; 6) clitellum girdle-shaped or gland cells absent between bursal slits and pre-middle ventrally; 7) coelomocytes without refractile vesicles; 8) spermatheca without diverticula and both ampullae broadly united; and 9) long spermathecal ectal duct without gland at the orifice.

Spiochaetopterus iheyaensis, a new species of Chaetopteridae (Annelida: Polychaeta) is described from 6 specimens collected by the Deep-Sea Research Vehicle Shinkai 2000 from the deep sea at Iheya Seamount, off Okinawa, Japan. The species is characterized by the coloration of the ventral shield of the anterior region (region A), by having one or two pairs of large cutting chaetae on the fourth chaetiger (A4), and by the morphology of A4 modified cutting chaetae (with inflated semi-circular and pear-shaped in upper view, head lacking teeth), having 2 middle region (region B) chaetigers, and a slender, annulated tube. The new species is compared to Pacific Spiochaetopterus, particularly the ultrastructure of the A4 chaetae.