Records of chimaeroid fishes (Holocephali: Chimaeriformes) from the Pacific coast of Costa Rica, with the description of a new species of Chimera (Chimaeridae) from the eastern Pacific Ocean.

A new species of Chimaera Linnaeus 1758 is described from three specimens collected from off the Pacific coasts of Costa Rica and Peru. Chimaera orientalis n. sp.

A new fish, Peristedion nesium (Scorpaeniformes: Peristediidae) from Isla del Coco, Costa Rica.

Several expeditions in recent years to Isla del Coco have increased the total number of species of fishes known from the island. Several of these species have been described as new endemics (Bussing 1983, 1990, 1991a, 1991b, 1997). During the 1972 R/V Searcher Expedition to Costa Rica several trawl collections were made around Isla del Coco.

Astyanax cocibolca, a new characid (Pisces: Ostariophysi) from Lake Nicaragua, Central America.

Astyanax cocibolca, a small filter-feeding species is a new characid species endemic to Lake Nicaragua. It is distinguished from the syntopic Astyanax aeneus by its high gill raker count, slender body, upturned snout, long maxillary bones, conical outer premaxillary teeth, lower number of scales above lateral line, more intense black lateral band, smaller size, and trophic niche partitioning. At present the new species utilizes the open-water habitat at least as a nursery where young can feed on the rich plankton population.

A new species of poeciliid fish, Poeciliopsis santaelena, from Peninsula Santa Elena, Area De Conservación Guanacaste, Costa Rica.

An undescribed freshwater fish was recently discovered during a biological inventory of Area de Conservaci6n Guanacaste, northwestern Costa Rica. This new species of Poeciliopsis is closely related to a group of widespread species of small spotted fishes designated as the Poeciliopsis gracilis complex in this study. The complex extends on both versants from southern Mexico to Nicaragua, and with this new finding, extends into Costa Rica.

Panbiogeographical analysis of Costa Rican freshwater fishes.

Track analysis and Parsimony analysis of endemicity (PAE) were performed to analyze the distribution pattern of Costa Rican freshwater fishes. A basic matrix (presence/absence) was prepared using the distribution of 77 freshwater fish. The data were analyzed with CLIQUE software in order to find generalized tracks (cliques).

Four new species of eastern tropical Pacific jawfishes (Opistognathus: Opistognathidae).

Three of four new jawfishes described herein have sexually dimorphic jaws and dichromatic maxillary markings: O. smithvanizi, with a simple nasal cirrus, buccal pigmentation and other traits similar to members of the O. macrognathus group, is known only from Isla del Caño, a continental shelf island off southern Costa Rica; O.