37 Fish described in 1866

Achondrostoma arcasii, termed the bermejuela, is a species of freshwater fish in the family Cyprinidae. It is found in the Douro River in northern Portugal and in rivers draining to both the Atlantic Ocean and the Mediterranean, including the Ebro River, in northern Spain where it is threatened by loss of habitat caused by the building of canals and the construction of dams, as well as by introduced predators and water pollution.

Achondrostoma oligolepis is a species of cyprinid fish. It is endemic to central and northern Portugal and known from between Limia and Tornada drainages, south of Douro. It occurs in the lower stretches of rivers and streams. It can grow to 25 cm (9.8 in) total length, although it typically measures about 15 cm (5.9 in) TL.

Anaecypris hispanica, the Spanish minnowcarp, is a small species of ray-finned fish species in the family Cyprinidae. It is the only living member of the genus Anaecypris. It is endemic to the Iberian Peninsula and is found in the basin of the Guadiana River in southern Spain and Portugal. Its natural habitats are rivers and intermittent rivers which are shallow, highly oxygenated, have a water temperature of no more than 25 °C and have a coarse stream bed. It is threatened by habitat loss. They grow to a maximum size of 60mm and live for three years.

Arrhamphus sclerolepis, the Northern snub-nosed garfish, is a species of halfbeak in the genus Arrhamphus found in coastal waters of the Indo-West Pacific around Papua New Guinea and Australia, and in the freshwaters of adjacent river systems. Considered a good game fish, but of little commercial value either as food or as an aquarium fish. This species is known to anglers in Australia as the snub-nosed gar. The species is distinguished from most other halfbeaks by the lower jaw being only slightly longer than the upper jaw.

The Australian bass is a small to medium-sized, primarily freshwater species of fish found in coastal rivers and streams along the east coast of Australia. It is a member of the family Percichthyidae and the genus Macquaria. Australian bass is an important member of the native fish assemblages found in east coast river systems. It is a predatory native fish and an extremely popular angling species. The species was simply called perch in most coastal rivers where it was caught until the 1960s, when the name Australian bass started to gain popularity.

Caulolatilus cyanops, the Blackline tilefish, is a species of tilefish native to the western Atlantic Ocean where they are found from North Carolina to the northern coast of South America. They inhabit the seafloor in areas with muddy or sandy substrates at depths of from 45 to 495 metres though they are usually found between 150 and 250 metres. They prey on invertebrates and smaller fishes. They can reach a length of 60 centimetres (24 in) TL though most are around 30 centimetres (12 in). The greatest recorded weight for this species is 11 kilograms (24 lb). This species is commercially important and is also sought after as a game fish.

Cladodus is an extinct genus of cartilaginous fishes in the family Cladoselachidae. As the name implies, they are a type of cladodont, primitive sharks with teeth designed to snag fish and swallow them whole, instead of sawing off chunks to swallow.

The climbing galaxias or kōaro is a fish of the family Galaxiidae found in Australia, New Zealand, and nearby islands. The name climbing galaxias is used in Australia, and koaro or kōaro in New Zealand. Further vernacular names include short-finned galaxias, broad-finned galaxias, Cox's mountain galaxias, and Pieman galaxias.

The eastern blue groper is a species of wrasse native to southeastern Australia from Hervey Bay in southern Queensland to Wilsons Promontory in Victoria. They occur in coastal waters, preferring rocky areas at a depth of about 40 m (130 ft). Juveniles inhabit beds of seagrass in estuaries. The diet of this species consists of invertebrates such as various molluscs, crabs, sea urchins, and cunjevoi. This species grows to a length of 72 cm (28 in) as adult males, while females are less than 60 cm (24 in) long. This species was sometimes sought as a game fish but this is now banned in New South Wales. In 1998, the eastern blue groper was made the state fish emblem of New South Wales.

Exocoetus obtusirostris, commonly known as the oceanic two-wing flyingfish or the blunt-snouted flyingfish, is a species of ray-finned fish native to the tropical and subtropical western Atlantic Ocean. It has the ability to glide above the surface of the water to escape from predators.

The false osman is an Asian cyprinid freshwater fish living in the highlands of Afghanistan, southwestern China, Iran, northern India, Kyrgyzstan, Pakistan and Tajikistan. Young individuals and small adults live in shallow streams and pools, while large adults inhabit the main river and lakes. It grows to 34 cm (13 in) in total length.

Galaxias olidus, the mountain galaxias, is a species of freshwater galaxiid fish widely found in southeastern Australia.

Darwin's slimehead, also known as the big roughy, is a species of fish in the slimehead family found widely in the Atlantic and Indo-Pacific oceans. This deep-sea species reaches a length of 60 cm (2.0 ft) and is mainly found at depths of 200 to 500 m (660–1,640 ft), but has been recorded between 9 and 1,210 m (30–3,970 ft). Based on broadly overlapping morphological features it sometimes includes G. japonicus as a synonym.

Gillaroo is a variety of trout which eats primarily snails and is only proven to inhabit Lough Melvin in Ireland.

The Steindachner's Angolan mormyrid is a species of elephantfish in the family Mormyridae being the only member of its genus. It is found only in the coastal river basins in Angola in Africa. It reaches a length of about 10 cm (4 in).

Iberochondrostoma lemmingii is a species of ray-finned fish in the family Cyprinidae. It is found in Portugal and Spain. It lives in the middle and lower reaches of rivers with slow current.

Labrisomus philippii, the Chalapo clinid, is a species of labrisomid blenny native to the Pacific coast of South America from Peru to Chile. This species can reach a length of 35 centimetres (14 in) TL and the greatest recorded weight for a specimen of this fish was 635 grams (22.4 oz). The identity of the person honoured by Steindachner in the specific name of this fish is unknown but it is thought to be one of the Chilean family of naturalists, the Philippis, Rodolfo Amando Philippi (1808-1904), the German-Chilean paleontologist and zoologist, his brother Bernhard Eunom Philippi (1811-1852) or Rudolfo's son, Federico Philippi (1838-1910).

Luciobarbus graellsii is a ray-finned fish species in the family Cyprinidae. It is here placed in Luciobarbus following the IUCN, but that genus is very closely related to the other typical barbels and perhaps better considered a mere subgenus of Barbus. The Andalusian barbel was formerly included in L. bocagei as subspecies.

Melanotaenia splendida, the Eastern rainbowfish, is a species of rainbowfish from the subfamily Melanotaeniinae which is found in Australia.

The mountain galaxias is a species complex of freshwater galaxiid fish found all over southeast Australia.

The ornamented flying fish, or beautyfin flying fish, is a species of flying fish of the genus Cypselurus in the family Exocoetidae. The British ichthyologist Albert Günther first described it in 1866 in his eight-volume Catalogue of Fishes (1859–1870).

Pachypanchax playfairii, the golden panchax, is a species of Aplocheilid killifish, the only species of freshwater fish endemic to the Seychelles, a group of islands in the Indian Ocean directly east of Tanzania, and the only member of its genus found outside of Madagascar. Within the Sychelles it is found only on the granitic islands. Here it occurs in small freshwater and brackish water streams, feeding on worms, crustaceans, insects and fish. An egg scatterer, the golden panchax breeds amongst floating water plants. This species is unusual in that the scales of the male become lifted during the breeding season, giving the skin a rough appearance. Unlike the true annual killifish, they live as long as similar fishes, a few years, 3 years is not uncommon 5 is unknown.

Parachondrostoma arrigonis is a species of cyprinid fish endemic to Spain only found in the Júcar River basin. Its natural habitat is rivers. It is threatened by habitat loss.

Parachondrostoma miegii is a species of cyprinid fish endemic to Spain, where it occurs in the basin of the Ebro and in one headwater of the Tagus. Its natural habitat is rivers. It is threatened by habitat loss.

Profundulus guatemalensis, the Guatemalan killifish, is a species of killifish from the family Profundulidae which is found in Central America in Honduras, El Salvador, Belize and Guatemala.

Pseudochondrostoma willkommii is a species of cyprinid fish. It is found in Portugal and Spain. Its natural habitats are rivers and water storage areas. It is threatened by habitat loss.

The rainbow goodeid is a species of fish in the family Goodeidae endemic to Mexico.

The rosy bitterling or Tairiku baratanago is a small freshwater fish belonging to the family Cyprinidae (carp), native to East Asia from the Amur River basin to the Pearl River basin.

The Salvin's cichlid, also known as the yellow-belly cichlid or tricolored cichlid, is a species of the family Cichlidae. It is found in rivers of the Atlantic slope of southern Mexico, Belize, and Guatemala.

The scaly osman is a species of cyprinid freshwater fish. It is native to Himalaya and the Tibetan Plateau of China, India, Nepal and Pakistan, ranging west to the Tien Shan Mountains and Central Asia. It is up to 70 cm (2.3 ft) in total length.

The slender barb or longbeard barb is a species of ray-finned fish in the genus Enteromius which has a wide distribution from the Democratic Republic of the Congo to South Africa.

The southern platyfish, common platy, or moonfish is a species of freshwater fish in family Poeciliidae of order Cyprinodontiformes. A live-bearer, it is closely related to the green swordtail and can interbreed with it. It is native to an area of North and Central America stretching from Veracruz, Mexico, to northern Belize.

Squalius alburnoides is a species of fish in the family Cyprinidae. It is found in Portugal and Spain. Its natural habitats are rivers and intermittent rivers. It may be threatened by habitat loss.

The Tibetan stone loach is a species of ray-finned fish in the family Nemacheilidae. The specific name is sometimes spelled stoliczkae but the original spelling used by Steindachner is stoličkai. It is found in southern and central Asia.

The golden topminnow is a fish of the genus Fundulus and is a United States native fish mostly distributed throughout the southeast, ranging from Kentucky and Ohio south into Florida. Although it has such a wide distribution throughout the south, the habitats and micro-habitats that it occupies do not differ much from one area of distribution to others. The golden topminnow is a small surface feeding fish that tends to reproduce late in the spring season and on into the early parts of the summer, and although the fry reach maturity fairly quickly the longevity of the golden topminnow is quite short. Because the golden topminnow is lower in the trophic level and is a small fish, it primarily feeds on small and/or drifting organisms at, or near the surface of, vegetated areas. This particular topminnow is not currently listed as an endangered species, nor does it have any particular type of management plan.

Zambezi bream, also known as dwarf bream, is a species of haplochromine cichlid which is found in river systems in southern Africa.