Among the 15 known genera of murine rodents endemic to the island of Sulawesi, is the shrew rat genus Echiothrix. Physically large (length of head and body  =  182–235 mm; weight  =  215–310 g) with a bicolored tail typically longer than head and body (100%–135% of head and body length), elongate hind feet (48–55 mm), large ears (31–35 mm), long and thin muzzle, spinous fur, and tiny molars relative to size of skull (length of molar row  =  12%–13% of occipitonasal length), Echiothrix was named and described in 1867 and through the years has been treated as monotypic or containing up to three species. Results from analyses of morphometric traits derived primarily from cranial and dental measurements document the presence of two species. Echiothrix leucura (Gray, 1867) is restricted to the northern peninsular mainland east of the Gorontalo region (00°31′ N, 123° 03′ E). This distribution is concordant with that of four other murids endemic to the northeastern tip of the northern peninsula: Bunomys fratrorum, Taeromys taerae, Rattus xanthurus, and R. marmosurus. Echiothrix centrosa Miller and Hollister, 1921 (Echiothix brevicula Miller and Hollister, 1921, is a synonym), is documented by specimens from the northern peninsula west of the Gorontalo region and in the central portion of the island; 19 other murine species are also known only from the core of Sulawesi. Whether the range of E. centrosa extends to the eastern, southeastern, and southwestern peninsulas is at present unknown. Echiothrix leucura has a more elongate skull compared with E. centrosa (greater lengths of skull, rostrum, diastema, and bony palate), a wider interorbital region, larger braincase, narrower bony palate and mesopterygoid fossa, shorter incisive foramina, and appreciably larger molars; the two species also differ in frequencies of particular molar cusps and cusplets. Both species of Echiothrix are nocturnal, terrestrial, and occupy habitats in tropical lowland evergreen rain forest. Natural history observations made in the field for Echiothrix centrosa show it to be primarily vermivorous; other natural history observations derived from field work in central Sulawesi are provided. One aspect of that natural history is the ectoparasitic load borne by E. centrosa. This shrew rat is host to at least four species of ticks (Haemaphysalis kadarsani, Haemaphysalis hystricis, Haemaphysalis sp. and Amblyomma sp.), a tiny fur mite (Listrophoroides echiothrix), mesostigmatid mites belonging to the genus Laelaps, currently undetermined chiggers, a flea (Farhangia quattuordecimdentata), and a new species of sucking louse described herein as Polyplax beaucournui. This louse has tibiotarsal claws adapted for grasping slender soft hairs in the pelage and not the wide host spines; female lice also attach their eggs only to these slender hairs. The closest relative of Echiothrix is probably Paucidentomys vermidax, another Sulawesian endemic shrew rat that is also vermivorous but lacks molars and has been collected only in montane forests. The present report documents morphological and distributional limits of species in Echiothrix, places one of those species in an ecological and parasitological landscape, and generally contributes to knowledge covering endemic murid species diversity and identifying unique zoogeographical areas on Sulawesi.