Trinius
Trinius (Trigno), a considerable river of Samnium, which has its sources in the rugged mountain district between Agnone and Castel di Sangro, and has a course of about 60 miles from thence to the Adriatic. During the lower part of its course it traverses the territory of the Frentani, and falls into the sea about 5 miles SE. of Histonium (Il Vasto). The only ancient writer who mentions it is Pliny (3.12. s. 17), who calls it flumen portuosum:
it is, indeed, the only river along this line of coast the mouth of which affords shelter even for small vessels.
From William Smith (ed.), Dictionary of Greek and Roman Geography. Text provided under a CC BY-SA license by Perseus Digital Library, http://www.perseus.tufts.edu, with funding from the National Endowment for the Humanities and Tufts University. Data accessed from https://github.com/PerseusDL/canonical-pdlrefwk/ on 17 October 2026.