Characidium litorale is distinguished from other congeners by the combination of the following characters: complete lateral line (vs. incomplete in C. interruptum, C. laterale, and C. rachovii); greater body depth at dorsal-fin origin 20.9-24.6% SL (vs. 9.3-15.8% SL in C. longum, 13.7-17.2% SL in C. pteroides, 14.2-18.9% SL in C. steindachneri); fewer lateral line scales 34-36 (vs. 38-40 in C. longum, and 37-40 in C. steindachneri); and fewer scales in the series between the anus and anal-fin origin 4-5 (vs. 8-10 in C. longum, and 6-8 in C. steindachneri); absence of a large blotch on caudal peduncle (vs. presence in C. bimaculatum); and absence of bands in distal part of anal fin (vs. presence in C. heinianum); and deeper caudal peduncle depth 10.6-12.1% SL (vs. 6.7-10.0% SL in C. heinianum). C. litorale of size ranges 2.65-3.27 cm SL differs from C. xanthopterum of size ranges 2.24-3.15 cm SL by having lower body depth (20.9-24.2% SL vs. 24.2-27.6% SL in C. xanthopterum), and from C. zebra of size ranges 2.46-3.22 cm SL by having fewer scales around caudal peduncle (12 vs. 14 in C. zebra), greater body depth at dorsal-fin (20.9-24.6% SL vs. 16.1-19.6% SL in C. zebra) and anal-fin origin (15.6-18.1% SL vs. 12.3-14.6% SL in C. zebra), deeper caudal peduncle (depth 10.6-12.1% SL vs. 8.9-10.6% SL in C. zebra), and by the shape of the longitudinal midlateral stripe (thin and restricted to the posterior half of the body versus wide and extending throughout the flank in C. zebra). Other conspicuous non-unique external characters useful in distinguishing C. litorale include the following: isthmus completely covered with scales; basicaudal spot well defined and isolated by a bright area; and markedly reticulated pigmentation pattern at upper half of body. There are slight differences in morphology among populations from the São João, Macaé and Imbé drainages: specimens from Rio São João frequently possess more secondary bars, and individuals from the Rio Macaé usually have a lower body depth. The secondary bars may be less evident or lacking in few specimens (13.6%) from Rio Imbé (Ref. 96085).