TRI´NIUS(Trigno), a considerable river of Samnium, which has its sources in the rugged mountain district between Agnoneand 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 (Plin. Nat. 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.
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