Family Plotosidae. Genus Euristhmus, Ogilby. Euristhmus, Ogilby, Proc. Linn. Soc. N.S. Wales, xxiv, 1, 1899, p. 154 (Plotosus elongates, Castelnau). This genus is distinguished from Cuidoglanis, Gunther, by the wide isthmus, which separates the gill-membranes; its axillary pore is also much smaller than that of C. Megastomus. Euristhmus Lepturus, Gunther. Long tailed Catfish. (Plate xxi, fig 1). Cuidoglanus lepturus, Gunther, Brit. Mus. Cat Fish, v., 1864, p. 28. Depth before the ventral fins 1.3 in the length of the head, and 8.5 in the length to the hypural joint; head 6.3 in the same. Head and body 2.1 in the length of the tail. Eye 3.07 in its distances from the end of the snout, and 2.3 in the interocular space, which is 3.6 in the head. Dorsal spine 2.5, pectoral spine 3.0 in the head. Dorsal fin 2.1, pectoral fin 1.9, and ventral fin 2.7 in the head.