A LEAF MIMICKING FISH. 1 



CARL H. EIGENMANN AND WILLIAM RAY ALLEN. 



Heckel, in Johann Natterer's "Neue Flussfische Brasilien's 

 nach den Beobachtungen und Mittheilungen des Entdeckers, " 

 described a small fish 3.5 inches long from a forest pool along 

 the Rio Negro. He named it Monocirrhus polyacanthus and 

 stated that at Marabitanas it was called pird-cda which means 

 leaf-fish. Marabitanas is less than one degree north of the 

 equator near the fiftieth degree of w r est latitude, in other words 

 about sixty miles south of the southern end of the Rio Cassiquiare. 

 No other specimens have been recorded. Gunther placed it 

 with Polycentrus to constitute the family Polycentridae. The 

 leaf-like appearance evidently impressed the Indians about 

 Marabitanas who were acquainted with it and had a name for it. 



During the Centennial Expedition of Indiana University, Dr. 

 Allen secured three specimens of the same, or of a similar species 

 from a brook near the Rio Itaya at Iquitos on the Peruvian 

 Amazon. 



The junior author reports that this fish was collected on 

 September 19, 1920, while a guest of Don Antonio Layet at his 

 hacienda, about six kilometers up the Rio Itaya from Iquitos. 

 It was found in a small, sluggish brook which flows over very flat 

 second bottom land, seldom inundated, and in the midst of dense 

 forest. 



There had not been much recent local rain, and there was only 

 a slightly perceptible trickle of current at the riffles. Most of the 

 brook was now reduced to quiet pools ten to fifteen feet across, 

 densely overhung by vegetation, and shaded except for an 

 hour or two at mid-day. The water was clear and of a slightly 

 brown color, the bottom brushy, and matted with fallen leaves. 



"Sr. Layet's servants had just introduced poison for me at the 

 riffles, allowing it to flow slowly into the pools. Others with 

 their long knives had made paths by which the low bank could 



1 Contribution from the Zoological Laboratory of Indiana University, No. 183. 

 " Ann. Wien Mus., 1840, II., p. 439. 



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