The genus Arctangia Wells is a poorly known group that consists of only the type species Thecocyathus nathorsti Lindström, 1900. The original description is the only documentation of the species. Including the first description of the genus Arctangia by Wells (1937), all of the later interpretations of the species represent only adaptations of Lindström's original report. The present paper gives the re-description of the type species and also provides the first photographic images of this species based on newly discovered material.

A common intertidal hoplonemertean species, Amphiporus nelsoni Sanchez, 1973, from Chile is re-described based on the investigation of material from the type locality and one other locality in Chile. The species is transferred to the genus Prosorhochmus Keferstein, 1862 (Prosorhochmidae) based on the presence of a dorsal epidermal fold, i.e., “prosorhochmid smile” on the bilobed head, truncated stylet basis, well-developed frontal organ with characteristic epithelial specialization, structure of the nephridial system and other characters of internal anatomy. Placement of this species into Prosorhochmus expands the geographical distribution of the genus, previously known only from the North Atlantic and Mediterranean, to the South Pacific. Interestingly, Prosorhochmus nelsoni (Sanchez, 1973) is characterized by separate sexes and oviparity, unlike all the other members of the genus, which combine hermaphroditism with ovoviviparity. We compare P. nelsoni to the other species of Prosorhochmus and reassess some of the morphological characters used in the systematics of the genus.

A new kinorhynch, Echinoderes spinifurca, is described from the Atlantic coast off Fort Pierce, Florida. The species is characterized by the presence of middorsal spines on segments 6 to 10 and lateral spines/tubules on segments 4 and 7–12. The tergal furca (tergal extension) is extraordinarily long, constituting 9.3–12.9 percent of the trunk length, and this distinct character makes it easy to distinguish the species from all other species of Echinoderes. Echinoderes spinifurca occurs in shell gravel and mixed shell gravel with sand, and coexists with Echinoderes horni, Zelinkaderes sp., and two undescribed cyclorhagid taxa.

Austrosignum fuegiae, a new species, is fully described on the basis of specimens collected in the shallow waters of the Beagle Channel. The genus Austrosignum Hodgson, 1910 is in need of revision, and the inclusion of A. fuegiae in this genus should be considered provisional. Austrosignum fuegiae is most similar to A. dentatum Winkler, 1994, which was previously known from the Magellan Strait and is herein recorded for the Beagle Channel for the first time. These two species have a head with bilobed frontal margin, short eyestalks, and mandibles with palps, a group of characters that is not shared by the type species of the genus, A. grande Hodgson, 1910.

A new species of Synalpheus from Punta Mita, Nayarit, Mexico, is described. The new species was collected from coral rubble at a depth of 3 m. Synalpheus lani is morphologically similar to S. superus Abele & Kim, 1989, S. sanjosei Coutière, 1909, and S. townsendi mexicanus Coutière, 1909, but can be distinguished by a more elongated major chela without a spine on the dorsodistal margin of the merus. The length/width ratios of merus, propodus, and dactyl of the third pereopod also separate the four species. From this group of similar species, the new species has been recorded sympatrically only with S. sanjosei.

A new species of Notopoma (Ischyroceridae) is described and illustrated from Ría Deseado, Santa Cruz Province, Argentina. Notopoma argentina, the first species of the genus reported from South America, can be distinguished from other known species of this genus by having, among other characters, a long carpus with its palm slightly concave on gnathopod 2 of large males. Jassa marmorata Holmes, 1903, another ischyrocerid species having worldwide distribution, is here reported from Argentina and Uruguay.

A new trapeziid crab species of the genus Hexagonalia Galil, 1986, whose congeners are typically symbiotic with stylasterid corals, is described from deep water off the Solomon Islands. Its association with a host remains unknown.

A single ovigerous female of Parapinnixa cortesi, a new species, was collected from the calcareous tube of an unidentified serpulid polychaete on Isla del Coco, Costa Rica. The new species most closely resembles P. glasselli Garth, 1939, P. hendersoni Rathbun, 1918, and P. nitida (Lockington, 1876), but it can be distinguished from these and all other members of the genus by the morphology of the chelae and the proportions of the carapace.

Two xanthoid crabs, Panopeus meridionalis Williams, 1984 and Eurypanopeus depressus Smith, 1869 are reported from Mar Chiquita, a coastal lagoon in the warm-temperate region of the southwestern Atlantic. This study documents the presence of a stable population of P. meridionalis in the lagoon, although there have been some sporadic reports of this species in the region before 2000. It reports the first finding of E. depressus in waters south of the Rio de la Plata estuary. The role of Rio de la Plata as a biogeographical barrier is briefly discussed.

A new species of crayfish from Camino a Olotla, Tlanchinol County, Hidalgo, Mexico, is described. Procambarus (Ortmannicus) hidalgoensis is most closely related to P. (O.) cuevachicae (Hobbs, 1941) and P. (O.) toltecae Hobbs, 1943, from which it can be distinguished by having a gonopod with a mesial process slightly flattened distally and directed caudodistally; a cephalic process slightly larger than the rest of the terminal elements, originating on the caudal surface; and a plate-like caudal process, exhibiting a strongly folded external part of the pleopod. The annulus ventralis in the new species is rhomboidal, with two strong crests, forming a deep V-shaped depression anteriorly, ending in a sinus in the middle region.

A new neoteuthid genus and species, Narrowteuthis nesisi, is described on the basis of two specimens with the following characters that are unique within the family: laterally compressed proximal manal suckers, short tentacular clubs relative to mantle length, and smooth sucker rings on arm suckers. It is also the only neoteuthid in which the proximal and distal manus regions of the club are approximately equal in length.

Synallactes laguardai is described from the southwestern Indian Ocean, South Africa, off Durban, at 409.5 m. This new species may be readily distinguished from all previously known species of Synallactes Ludwig, 1893 by the body wall ossicles whose perforations form a complex circular lattice-like network.

Symphurus ocellaris is described on the basis of a holotype (73.2 mm SL) and paratype (42.3 mm SL) collected in the environs of Coiba Island, Gulf of Chiriqui, Pacific Panama, at 24 m and 7.4 m, respectively. This species is distinguished from congeners by the combination of: a 1–3–4 pattern of interdigitation of dorsal-fin pterygiophores and neural spines (ID pattern), 12 caudal-fin rays, presence of an ocellated spot on the caudal fin in both sexes, 51 total vertebrae, 96–97 dorsal-fin rays, 80–81 anal-fin rays, 85–86 longitudinal scale rows, a pupillary operculum, unpigmented peritoneum, uniformly pigmented blind side, and ocular-side background coloration lacking prominent dark spots or conspicuous crossbands. Symphurus ocellaris is only the second known species in the genus characterized by a 1–3–4 ID pattern. Among eastern Pacific Symphurus, S. callopterus also has a 1–3–4 ID pattern and 12 caudal-fin rays, but lacks the ocellated caudal spot, has a different ocular-side pigmentation, and has higher, non-overlapping meristic features. The only other eastern Pacific tonguefish with an ocellated caudal-fin spot, S. fasciolaris, differs in having 10 caudal-fin rays, a 1–4–3 ID pattern, and ocular-side pigmentation featuring prominent spots and crossbands.

A new species of coral-dwelling gobiid, Gobiodon prolixus, is described on the basis of material from scattered localities in the Indo-west Pacific (Comores, Rodrigues, Chagos, Thailand, Vietnam, Ponape, Tonga, Rapa, and Tuamotu). Gobiodon prolixus is distinguished from congeners by its unique, more elongate body shape in combination with five narrow blue bars on the lateral surfaces of the head. That pigmentation pattern is otherwise found in G. quinquestrigatus and G. rivulatus, species with which the new species has been confused in the past.

A new species of frog is described from Rondônia, Brazil. The new species shares most features with the genus Leptodactylus, although externally it resembles species of Physalaemus as much as species of Leptodactylus. The new species is provisionally assigned to the genus Leptodactylus, the definition of which must be expanded to include an areolate belly and small osteoderms lying above the vertebral column in order to accommodate the new species. The new species is known only from a single cerrado enclave in a predominantly Amazonian rainforest landscape.

We demonstrate that USNM 2040 and not UMMZ 3781 (originally part of lot USNM 4500) was most likely the holotype of Tantilla gracilis. The type specimens of Tantilla nigriceps have been lost or destroyed. It is not possible to determine from the original description of Tantilla nigriceps if this name represents what is currently known as T. nigriceps or T. hobartsmithi. In order to attribute the name T. nigriceps firmly to the species as currently recognized, we designate a neotype.

A new mouse species in the genus Habromys, H. schmidlyi, from the Mexican states of Guerrero and Estado de México, is described. Closest affinities of the new species are with H. simulatus and H. chinanteco, although strong morphometric differentiation and ample geographic isolation are evident. Penis structure and the basic karyotype of the new species are described.

Based on morphological and morphometric comparisons, a new species of Hylomyscus, H. arcimontensis (Muridae: Murinae), is identified from Mount Rungwe and the Eastern Arc Mountains of central and eastern Tanzania. The new species is confined to wet montane forests of these mountains and represents another vertebrate endemic to the Tanganyika-Nyasa Montane Forest biotic region (sensu Moreau 1966). It is most closely related to H. anselli, a form described from mountains in northern Zambia as a subspecies of H. denniae and here elevated to species rank. Morphological evidence supports the view that the nominal species H. denniae is a composite of several species whose interrelationships and differentiation patterns indicate two species complexes: the H. denniae group centered in Central East African mountains (Burundi, Kenya, Rwanda, Uganda, Zaire) and the H. anselli group distributed across more southern mountains (Angola, Malawi, Tanzania, Zambia).