298 
ACTINOPTERYGII. 
GeBus TETRAGONOPTERUS, Cuvier. 
[Eegne Animal, vol. ii. 1817, p. 166.] 
Trunk laterally compressed, but with rounded ventral border. 
Anterior teeth stout and incisor-like, lateral teeth smaller ; those 
of dentary and premaxilla laterally compressed and notched, the 
former in single and the latter in double series. Dorsal fin median 
and short-based ; anal fin more or less extended ; caudal fin forked. 
Scales of moderate size, not serrated; lateral line conspicuous. 
Existing species in the freshwaters of tropical America. 
Tetragonopterus avus, A. S. Woodward. 
[Plate XVir. fig. 1.] 
1898. Tetragonopterus avus, A. S. Woodward, Rev. Mus. Paulista, vol. hi. 
p. 66, fig. 3. 
Type. Imperfect fish j Bri4ish Museum. 
A species attaining a length of about 0*2. Length of head with., 
opercular apparatus about equal to maximum depth of trank, which 
is contained slightly more than four times in the total length of the 
fish. Vertebrae about 20 in the abdominal, 22 in the caudal region. 
Dorsal fin with 9, anal fin with about 22 rays, the former com¬ 
pletely in advance of the latter. 
Form. ^ Log. Tertiary Lignite : Taubate, Province of San Paulo, 
Brazil. ’ 
P. 9222. Type specimen, shown ofnat. size in PI. XVII. fig. 1. 
Presented hy John Gordon., Esq.., 1900. 
P. 9223-25. Twenty-five imperfect specimens, mostly larger than 
the type. Presented hy John Gordon, Esq., 1900. 
P. 9013. Imperfect fish. By exchange, 1898. 
Tetragonopterus ligniticus, A. S. Woodward. 
[Plate XVII. figs. 2, 3.] 
1898. Tetragonopterus ligniticus, E. S. Woodward,/oc. eit.p. 67, figs. 4, 5. 
Type. Imperfect fish ; British Museum. 
A smaller fish than the preceding, of comparatively slender pro¬ 
portions. Vertebrae about 38 in total number, 20 being caudal. 
Pectoral fins relatively large, when adpressed reaching beyond the 
origin of the small pelvic fins. Dorsal fin with 8 or 9 rays, directly 
