2 NEW SPECIES OF TETRAPHYLLIDEAN CESTODES IN HIMANTURA-PACIFICA (CHONDRICHTHYES, MYLIOBATIFORMES, DASYATIDIDAE) FROM THE NORTHWEST COAST OFCOSTA-RICA

TWO new species of tetraphyllidean cestodes inhabiting Himantura pacif ica from the northwest coast of Costa Rica are apparently most closely related to species inhabiting Himantura schmardae from the Atlantic c oast of Colombia. Acanthobothroides pacificus n. sp. differs from Acan thobothroides thorsoni, the only other species in the genus, primarily by having smaller lateral (98-123 mu m rather than 168-198 mu m long) and medial (handles 92-116 mu m rather than 162-168 mu m long) hooks, and more testes (up to 125 rather than up to 97) per proglottis. The generic diagnosis of Acanthobothroides is modified to include the pres ence of a small inner prong on the large medial bothridial hooks. Rhin ebothrium geminum n. sp. and Rhinebothrium magniphallum are the only 2 species in the genus possessing unusually long cirrus sacs, extending from the genital atrium all the way to the ovarian isthmus; R. geminu m averages 12 (12-14) loculi per bothridium and 11 (9-12) testes, wher eas R. magniphallum averages 17 (16-18) loculi and 14 (10-16) testes p er proglottis.