• Wide Form: Shell length up to 33 mm, mean w/1 ratio 0.79, mean h/1 ratio 0.37; com-pressed form mean w/1 ratio 0.56, mean h/1 ratio 0.25. Shell wide and straight at the pos-terior, narrower and rounded at anterior end. The apex is high above or in front of the posterior margin. Septum edge straight or slightly curved. Ground colour yellow-brown or olive-brown with black/brown markings, which form yellowish triangles or tongues. Interior white/gray and septum often yellowish. The two muscle scars are darker and often prominent. Males and females are approximately the same size and are present in equal numbers. Operculum: Nearly square, pink-orange with a clear horn at the posterior margin. Anterior rib angled slightly inwards.
• Compressed Form: Shell fragile, narrow, pointed and with apex outside shell margin. Back ground colour yellow/brown with black or purple longitudinal lines or with lines and triangles. The septum is deep with a curved margin. Operculum: fragile, yellow and rectangular.

This species has previously known as Septaria lineata but it is not synonymous with LAMARCK’S S. tesselatallineata. The Mann-Whitney U test showed that the shells of S. livida were significantly wider than those of S. tesselata. The males are the same size while S. tesselata males are sometimes smaller than the females, and S. livida has short (8 mm long) spermatophores while S. tesselata has comparatively long ones (20 mm long). In the wide form, the shell apex of S. livida is on or outside the shell margin unlike that of S. tesselata.
REEVE'S Navicella livida was the oldest type conforming to the characteristics of this species. REEVE'S type closely resembles specimens I have collected from mouths of rivers and streams in Viti Levu and Vanua Levu, Fiji. The compressed form has also been given names (N. picturata and N.francoisi) but these are not valid as intermediate specimens between the two extremes, wide and compressed, can be found.
The wide form of S. livida was thought by STARMUHLNER (1976) to be a form of S. lineata which RECLUZ (Le Guillou) 1841 had described as Navicella apiata. STARMUHLNER called this wide form S. lineata f. apiata. However RECLUZ (1841) gave the locality of N. apiata as Noukahiva and mistakenly placed it in the Fiji islands. Nuka Hiva is an island in the Marquesas Archipelago (French Polynesia). The types (10 syntypes MHNG, 3 syntypes MNHN) from Nuka Hiva are similar to those recently collected by O. FOSSATI from Nuka Hiva, Marquesas Islands. FOSSATI ET AL. (1992) refers to this species as Septaria porcellana, but S. apiata is a valid species differing from both S. porcellana and S. livida.

Range: Has a restricted range and has only been reported from Viti Levu, Vanua Levu, Ovalau (Fiji) and Vanuatu. In brackish water and in tidal parts of rivers and streams. Wider form found on stones, rocks and concrete bridge abutments in fast flowing water. Compressed form found on sticks, bamboo, grass stalks and floating wood in quiet tidal backwaters. Intermediate forms are found on bamboo and logs.