204 MEMOIRS OF THE CARNEGIE MUSEUM 



Sides everywhere lightly peppered with ehromatophores ; an hour-glass-shaped 

 dark bar across the base of the caudal. 



Ageneiosus Lacepede. 



Ageneiosus Lacepede, Hist. Nat. Poiss., V, 1805, 132 (armatus); IX, 167. 

 Pseudageneiosus Bleeker, Nederl. Tijdschr. Dierk., I, 1863, 108 (davalla). 

 Ageniosus Gunther, Catalogue, V, 1864, 191 (sp.). 



Type, Ageneiosus armatus Lacepede. 



Maxillary barbels only; air-bladder minute, concealed under the peritoneum 



and largely covered with bone; no pseudo-tympanum. Snout much longer than 



the eye. 



Key to the Guiana Species of Ageneiosus. 



a. Caudal deeply forked. 



6. A. 45; back with obscure marblings; maxillary band of teeth comma-shaped, the teeth large; 

 dorsal and pectoral spines slender, pungent; origin of anal a little nearer base of middle 

 caudal rays than the rictus; pectorals not reaching ventrals. Head 4: P. 1,14; Br. 9. 



guianensis. 



aa. Caudal emarginate; dorsal and pectoral rays smooth on posterior margin, the pectoral ray not 



pungent. 



c. Dorsal spine strong, sinuate, rough or spinous in front; profile steep, concave, origin of anal 



equidistant from base of middle caudal rays and anterior margin of eye; pectoral falcate, 



the first ray reaching beyond origin of ventrals; head 3.66; P. 1,14; Br. 9; A. 34, dark 



above, lighter below brevifilis. 



cc. First dorsal ray not spinous; profile nearly straight and horizontal; origin of anal a little nearer 

 origin of pectoral than to base of middle caudal rays; pectoral rounded, not reaching ven- 

 trals; head 3.33; P. 16; Br. 10; A. 29. Conspicuously marked with light and dark. 



marmoratus. 



75. Ageneiosus guianensis sp. nov. (Plate XXI, fig. 2.) 



Type unique, a female, 175 mm. Wismar. (Carnegie Museum Catalog of 

 Fishes No. 1712a.) 



Head 4; depth 5.5; D. 1,6; A. 45; V. 8; P. 1,14; Br. 9; eye 3 in snout, 6 

 in head, 3.5 in space between the eyes below. 



Profile concave, not very steep, snout much depressed; width of head 1.4 in 

 its length; length of snout less than interocular width by about an orbital diameter; 

 fontanel reaching above middle of eyes, the groove considerably farther; cleft of 

 mouth 3 in the length of the head; half the maxillary barbel osseous, its tip reaching 

 rictus; premaxillary band of teeth comma-shaped, widest in front, its width half 

 the length of the eye, the teeth comparatively large. Gill-openings extending 

 to below the posterior margin of the eye, the space between them about equal to 

 the diameter of the eye. 



