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Show 1903.] FISHES FROM RIO JANEIRO. 63 Air-bladder large, with two long lateral horns anteriorly and with a series of compartments along each side: anteriorly attached by a strong unpaired muscle running forward above the oesophagus. MYLACRODON GOELDII, sp. nov. (Plate VII.) Depth of body 2^-24- times in total length, length of head 3|- 35- times. Snout as long as eye, the diameter of which is 4 times in the length of head, interorbital width 3| times. Lower jaw included within the upper; maxillary extending to below anterior quarter of eye ; praeorbital entire. 12-13 gill-rakers on lower part of anterior arch. Sc. 55-60 r^-rr; upper part of head, cheeks, and opercles scaly; snout, jaws, and praeorbital naked. D. X I , I 13, commencing somewhat behind the axil, first spine very small, second short, third longest and equal to |-§ the length of head, thence decreasing; anterior soft rays longest, equal to seventh spine. A. Ill 10, first spine short, third |-f of the length of second, which is equal to half the length of head. Pectorals scaly at the base, §-| the length of head, ventrals a little longer, not extending to vent; caudal strongly emarginate. Dark grey above, silvery below, fins blackish. Description based on two examples from Rio Janeiro, 225 and 230 m m . in total length. GERRIDJE. The East Indian genera Gazza Ruppell and Liognathus Lacep. {Equula Cuv.), until now placed with or near the Carangida?, are without doubt very nearly allied to Gerres, which they most closely resemble not only in external features but also in their internal anatomy. The relations of the genera of this family are shown in the subjoined key :- A. Scales moderate or large; gill-membranes free from the isthmus. D. IX-X 10; A. II-III 7-9 1. Gerres Cuvier. D. IX-X 15-16; A. V 13-14 2. Pentaprion Bleeker. B. Scales small; gill-membranes narrowly joined to isthmus; D. VIII 15-16. A. Ill 14. Teeth in jaws minute 3. Liognathus Lacepede. Teeth in jaws rather strong, compressed, pointed... 4. Gazza Ruppell. The distinction of the species of the genus Gerres is a matter of some difficulty. Dr. Goeldi's collection includes examples of a Gerres belonging to the section with praeoperculum and praeorbital serrated and with dark longitudinal lines along the rows of scales, and which I identify with G. patao Poey. Nearly all the American species of this section resemble each other very closely in proportions of the head and body, size of the eye, extent of the mouth, and number of scales and fin-rays; and it appears that the most constant characters which can be used for specific distinction are the number of gill-rakers, the length of the second |