ANNOTATED LIST OF THE SPECIES 383 
Type: Monocirrhus polyacanthus Heckel 
Rios Negro, Cupai; Guiana; Maranon 
Spiny rayed fishes of small size; body extremely compressed; dorsal and anal 
fins long with serrate margins, erect; soft dorsal and soft anal fins with vertical 
bases and hyaline, similar in both shape and color to the caudal; snout very long 
and sharply pointed; the mandible extending beyond snout, with a barbel; pre- 
maxillary with a long spine equal in length to the mandible; eye large, 4 in the head. 
492. MonocrRRHUS MIMOPHYLLUS Eigenmann and Allen 
Monocirrhus mimophyllus Eigenmann and Allen, 1921, Biol. Bull., XLI, 5, 301-305, figs. 1-3. 
Monocirrhus polyacanthus Fowler, 1939 (1940), Proce. Acad. Nat. Sci. Phila., XCI, 279, one, 71 mm.. 
Contamana. 
This specimen may belong here, as should be expected. 
15715, 3, 44-51 mm., to base of caudal, brook near Rio Itaya, Iquitos, Allen, September, 1920. 
A leaf-mimicking species of spiny-rayed fishes was described by Heckel in 
1840 (Johann Natterer’s Neue Flussfische Brasiliens). It was given the name 
Monocirrus polyacanthus, and later joined with Polycentrus to form the family 
Polycentridae, by Giinther. Scientifically it then went into complete desuetude 
for eighty years, although Dr. Myers informs me it was later rediscovered in Guiana 
and reported in certain aquarium journals, he himself having noted its occurrence 
at Rockstone and in the Essequibo. 
On account of the imperfect original description, without any illustration, 
we were uncertain as to the exact identity of our specimens with Heckel’s species. 
The wide distance separating our locality from the original source on the Rio 
Negro, a thousand miles to the eastward, made reasonable the assumption that 
they were not identical, even though similar. Hence the paper of 1921 describing 
our three specimens as M. mimophyllus. As far as one could tell from Heckel’s 
account, the identity might still be uncertain. 
Meanwhile, since 1921, the leaf-mimic has again come to light in the collec- 
tions of dealers in tropical fishes, imported into Germany and thence to the United 
States. Here it is reported as having been successfully propagated in aquaria, 
and its habits much more fully described. I have unsuccessfully attempted to 
procure specimens of these importations for comparison with our types. Mr. 
Innes’s halftone of polyacanthus appears very similar (Innes, 1933; ibid, 1935). 
However, the source of his material is not made known. The source of com- 
mercial collections is usually very indefinite. Whether the commercial species of 
unknown source is the same as MW. polyacanthus or mimophyllus, or both, or neither, 
is not yet positively demonstrated. 
Dr. Myers has examined a good series of Monocirrhus from the dealers. He 
assures me that there is but one species, polyacanthus. He does not state where 
the specimens came from originally. He is sure our specimens are not different 
in any respect. 
However, the Innes photographs (1933, p. 7, and 1935, p. 335) both clearly 
