34 
Indiana University Studies 
contact with the preopercle below; postorbitals very feeble; 
origin of the dorsal equidistant from the tip of the snout and 
the base of the caudal ; origin of the anal under the middle of 
the dorsal; anal emarginate; pectorals reaching the basal 
fourth of ventrals; ventrals slightly beyond origin of anal; 
first twelve anal rays with a basal sheath. 
A distinct humeral band; all but the first 2 and the last 
dorsal rays black except at the base ; caudal with a broad black 
bar; ventrals tipped with dark. 
Cheirodon piaba Liitken. 
17210, 31, 28-35 mm., Reyes. Nov., 1921. 
17211, 36, 32-36 mm., Lagoons, Lake Rogoagua. Nov., 1921. 
17212, 38, 18-27 mm., Huachi. Aug., 1921. 
17213, 149, 28-36 mm., Cachuela Esperanza. Mar., 1922. 
Odontostilbe paraguayensis Eigenmann & Kennedy. 
17202, 199, 36-52 mm., Popoi River, Upper Beni. Sept., 1921. 
17203, 97, 34-50 mm., Rio Iniqui, Upper Beni. Sept., 1921. 
17204, 207, 30-40 mm., Rurrenabaque. Nov., 1921. 
17205, 165, 18-58 mm., Huachi. Aug., 1921. 
17206, 9, 38-40 mm., Tumupasa. Dec., 1921. 
17207, 6, 35-40 mm., Ixiamas. Dec., 1921. 
Heretofore described only from the Paraguay basin. 
Monotocheirodon Eigenmann & Pearson, gen. nov. 
No adipose; lateral line complete; teeth five-pointed; pre- 
dorsal area scaled; no conspicuous tactile papillae about the 
head; anal short; caudal with a few large scales; suborbital in 
contact with the preopercle below ; maxillary and premaxillary, 
each with four similar teeth forming a continuous, not angu- 
lated series ; teeth all contracted at the base, expanded toward 
the free end; interhsemals feeble. Allied to Cheirodon and 
Odontostilbe. 
Monotocheirodon pearsoni Eigenmann. sp. nov. Plate XI, 
fig. 1. 
15348, 10 cotypes, largest 38 mm., Espia, 3,080 feet. July, 1921. 
17333, 12, 32-44 mm., Rio Iniqui, Upper Beni. Sept., 1921. 
17334, 3, 36-38 mm., Rio Colorado, Lower Bopi. Sept., 1921. 
17335, 2, 30 and 35 mm., Tumupasa. Dec., 1921. 
General appearance of a Creagrutus. 
Head 4.25; depth 3.75 to 4.25; D.10; A. 11 to 13; scales 4 or 
