Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. Săgăris, is; Săgărĭus, ii; Să-gĭārĭus, ii; and Sangărĭus, ii, m., a river in Phrygia and Bitnynia, which empties into the Propontis, now the Sacari or Sacaria.
Form Sagaris, Ov. P. 4, 10, 47; Mart. Cap. 6, § 687 sq.: Sagarius, Sol. 43, § 1: Sagiarius, v. 1. Plin. 6, 1, 1, § 4: Sangarius, Liv. 38, 18, 8.
Hence,
Sangărĭus, ii, v. Sagaris.