THE AMERICAN TETRAGONOPTERINAE. 123 
orbital completely covering cheeks. No interpolated rows of teeth; anal 
with a basal series of scales along its whole length. 
Origin of dorsal midway between snout and base of caudal; ventrals reach- 
ing anal, pectoral extending beyond base of ventrals. 
A vertical humeral spot over fourth and fifth scales of the lateral line. 
“Closely related to the preceding species, though apparently differs in 
the smaller head and deeper body” Fowler. 
5. Marxrana Higenmann. 
For Edward Laurens Mark. 
Markiana Etcenmann, Smithsonian misc. coll. quart., 1903, 45, p. 145. 
Tyrr.— Tetragonopterus nigripinnis Perugia. 
Related to Moenkhausia and Gymnocorymbus, from which it differs in the 
squamation and the abbreviated caudal; the scales are crenate, very regularly 
arranged, becoming gradually smaller below the lateral line, the series extending 
about halfway up on the anal. 
Compressed, deep, with a regularly arched ventral outline, the dorsal regu- 
larity being interrupted at the nape, the profile concave over the eyes. Head 
short, broad; an occipital fontanel continued as a groove on the occipital crest, 
a frontal fontanel extending forward to middle of eye; mouth small, the small 
maxillary nearly vertical, scarcely reaching the eye, slightly slipping under 
the preorbital; cheeks covered by the suborbitals. No maxillary teeth; outer 
row of premaxillary with triangular cutting edge, scarcely notched; inner 
teeth very heavy, with a few points arranged in a crescent; three anterior teeth 
of the mandible heavy, the fourth much smaller. Gill-membranes free from 
isthmus, slightly united to each other; gill-rakers setiform, about twelve on the 
lower arch; dorsal over origin of anal; margin of anal convex; adipose well 
developed; lateral line nearly straight, near the middle of the body. Nares 
together; tongue fleshy, adnate. 
Hasrtat.— Guiana and La Plata. 
Key to the Species. 
a. A dark caudal spot; pectorals dark, extending much beyond origin of ventrals; depth 2.33; head 
Dida OWA TA4 A BCAlER i —OS—1, 60 LO! arc spsievslsceislere vie ov cldleievs ee stelow epee e 1. nigripinnis (Perugia). 
aa. No caudal spot; uniformly silvery; A. 40; scales 7.5-41-7 to the ventral..2. geayi (Pellegrin). 
