ABSTRACT: A revision of the shore-fly genus Hydrochasma Hendel. The species of the genus Hydrochasma Hendel are revised, including 27 new species (type locality in parenthesis): H. andeum (Ecuador. Guayas: Boliche (02°07.7'S, 79°35.5'W)), H. annae (United States. Utah. Grand: Swasey Beach (15.3 km N Green River; 39°07'N, 110°06.6'W; Green River; 1255 m)), H. capsum (Ecuador. Orellana: RíoTiputini (0°38.2'S, 76°8.9'W)), H. castilloi (Ecuador. Loja: Catamayo (03°59'S, 79°21'W)), H. crenulum (Peru. Cuzco: Paucartambo, Atalaya (Río Alto Madre de Dios; 12°53.3'S, 71°21.6'W; 600 m)), H. denticum (Ecuador. Orellana: Río Tiputini (0°38.2'S, 76°8.9'W)), H. digitatum (Peru. Madre de Dios: Diamante (Río Alto Madre de Dios; 12°19.9'S, 70°57.5'W; 400 m)), H. distinctum (Costa Rica. Limón: Parque Nacional Barbilla, Sector Casas Negras, (10°0.8'N, 83°28.1'W; 300 m)), H. dolabrutum (Dominican Republic. Barahona: Barahona (18°12'N, 71°5.3'W)), H. edmistoni (Dominican Republic. Azua: near Pueblo Viejo (18°24.8'N, 70°44.7'W)), H. falcatum (Peru. Madre de Dios: Río Manu, Erika (near Salvación; 12°50.7'S, 71°23.3'W; 550 m)), H. glochium (Dominican Republic. Peravia: San José Ocoa (10 km NE; 18°35'N, 70°25.6'W)), H. kaieteur (Guyana. Kaieteur Falls (05°10.5'N, 59°26.9'W)), H. lineatum (Trinidad and Tobago. Trinidad. St. George: Filette (1 km SE; 10°47'N, 61°21'W)), H. miguelito (Honduras. Cortés: San Pedro Sula (8 km S; 15°25.7'N, 88°01.4'W)), H. octogonum (Ecuador. Manabí: Pichincha (01°02.7'S, 79°49.2'W)), H. parallelum (Trinidad and Tobago. Trinidad. St. Andrew: Lower Manzanilla (16 km S; 10°22'N, 61°01'W)), H. peniculum (Dominican Republic. Pedernales: Pedernales (18°01.8'N, 71°44.7'W)), H. rictum (Honduras. Cortés: San Pedro Sula (8 km S; 15°25.7'N, 88°01.4'W)), H. robustum (Brazil. São Paulo. Ubatuba, Praia Puruba (23°21'S, 44°55.6'W; beach)), H. sagittarium (Trinidad and Tobago. Tobago: St. John: Parlatuvier (creek; 11°17.9'N, 60°35'W)), H. simplicum (Costa Rica. Limón: Parque Nacional Barbilla, Sector Casas Negras, (10°01.2'N, 83°26.2'W; 300 m)), H. sinuatum (Belize. Stann Creek: Mullins Creek (17 km N Dangriga; 17°06.2'N, 88°17.8'W)), H. spinosum (Costa Rica. Limón: Westfalia (4 km S; 09°54.5'N, 82°59'W; beach)), H. urnulum (Dominican Republic. Puerto Plata: Río Camu (14 km E Puerto Plata; 19°41.9'N, 70°37.5'W)), H. viridum (Guyana. Karanambo, Rupununi River (ox bow; 03°45.1'N, 59°18.6'W)), H. williamsae (Belize. Stann Creek: Mullins River (17 km N Dangriga; 17°06.2'N, 88°17.8'W)). All known species are described with an emphasis on structures of the male terminalia, which are fully illustrated. Detailed locality data and distribution maps for all species are provided. A lectotype is designated for Discocerina incisum Coquillett and Hydrochasma zernyi Hendel. For perspective and to facilitate genus-group and species-group recognition, the tribe Discocerinini is diagnosed and a key to included genera in the New World is provided.
