Species described (32):
- Algansea affinis Regan, 1906, synonym
- Algansea stigmatura Regan, 1907, synonym
- Amiurus meeki Regan, 1907, synonym
- Tetragonopterus angustifrons Regan, 1908 (Astyanax), valid
- Atherinichthys sallei Regan, 1903 (Atherinella), valid
- Brycon guatemalensis Regan, 1908 (Brycon), valid
- Centropomus altus Regan, 1907, synonym
- Centropomus argenteus Regan, 1904, synonym
- Centropomus atridorsalis Regan, 1903, synonym
- Characodon geddesi Regan, 1904, synonym
- Cichlasoma biocellatum Regan, 1909, synonym
- Cichlosoma gadovii Regan, 1905, synonym
- Cichlosoma sexfasciatum Regan, 1905, synonym
- Cichlosoma robertsoni Regan, 1905 (Cribroheros), valid
- Elops affinis Regan, 1909 (Elops), valid
- Gambusia yucatana Regan, 1914 (Gambusia), valid
- Herichthys geddesi Regan, 1905, synonym
- Heterophallus rachovii Regan, 1914 (Heterophallus), valid
- Mollienesia gracilis Regan, 1913, synonym
- Moxostoma mascotae Regan, 1907 (Moxostoma), valid
- Cichlosoma multifasciatum Regan, 1905 (Parachromis), valid
- Paraneetroplus bulleri Regan, 1905 (Paraneetroplus), valid
- Mollienesia velifera Regan, 1914 (Poecilia), valid
- Pseudoxiphophorus bimaculatus var. taeniatus Regan, 1905, synonym
- Pseudoxiphophorus pauciradiatus Regan, 1904, synonym
- Rivulus godmani Regan, 1907, synonym
- Heros octofasciatus Regan, 1903 (Rocio), valid
- Sicydium multipunctatum Regan, 1906, synonym
- Heros (Heros) callolepis Regan, 1904 (Thorichthys), valid
- Xiphophorus brevis Regan, 1907, synonym
- Xiphophorus rachovii Regan, 1911, synonym
- Xiphophorus strigatus Regan, 1907, synonym
Genera described (5):
- Brachyrhaphis Regan, 1913, valid
- Heterophallus Regan, 1914, valid
- Paraneetroplus Regan, 1905, valid
- Poeciliopsis Regan, 1913, valid
- Priapella Regan, 1913, valid