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Dorsal-fin rays 11–13. Anal-fin rays 28–33, usually 29–32. Pectoral-fin rays 9–11. Vertebrae 43–45, including 19 anal vertebrae. Gill rakers 6 + 12, very rarely 7 + 12. Pyloric caeca 7 (based on 3 specimens). Peritoneum light with scattered clusters of melanophores, particularly dense in the anterior part of the cavity; anal opening not surrounded by black ring. When SL is greater than 100 mm, SL 4.7–5.5 times greater than head, decreases with growth; in fish with SL 76 mm, the head is 4.3 times smaller than SL. Eye diameter approximately equal to width of interorbital distance. Body depth at SL greater than 100 mm contained 6.6–7.8 times in SL, decreases with growth; at SL of 76 mm contained 6.4 times in SL. Photophores: OV and VAL at same level; VAV and VAL 8 each; 1st or 2nd AC slightly raised; AC 22–23, including 16–18 above anal fin.
Polymetme elongata is known from the waters of Japan, East China Sea, and from the Philippine Islands.
Parin N, Borodulina O. 1990. Survey of the genus Polymetme (Photichthyidae) with a description of two new species. Voprosy Ikhtiologii 30(5):733–743.
The following morphologic description of the genus is based on Parin and Borodulina (1990). Body elongate, vertebrae 42-46. Eye normal. Mouth large, two rows of premaxillary teeth. Branchiostegal rays 13–14. Gill rakers 15–19, typically 16 to 18. Dorsal-fin rays 10–13 (14), Anal-fin rays (25) 27–34. Pectoral-fin rays 9-11. Pelvic-fin rays 7. Pelvic fins far anterior to the dorsal-fin origin. Origin of anal fin below the end of the base of the dorsal fin. Adipose fin present. Photophores: ORB 1, by the anterior margin of the orbit. OP 3. SO 1. BR 9–10. IV 21, 10th slightly raised; VAV 8–9; AC 22–25, of them, 15-19 above the anal fin, anterior 2 may be slightly raised; IC 50–54. OV 9; VAL 8–9, anterior 1 or 2 may be slightly raised; OA 17-18.
Maximum length 184 mm.
Southeastern Pacific, 24°56'S, 88°32'W, depth 580–564 meters.
Holotype: ZIN 49576.
