Loma embiotocia n. sp. is described from the gills of shiner perch (Cymatogaster aggregata) from waters off Vancouver Island, British Columbia, Canada. Highest prevalence at a site was 15% and greatest intensity was 583 xenomas per fish. Xenomas averaged 0.13 mm in diameter (0.06-0.16 mm) and contained ovoid spores 4.8 x 2.6 (4.0-5.0 x 2.0-3.0) microns. Sporogonic stages were dispersed throughout the xenomas. The xenoma wall was smooth lacking invaginations into the cyto plasm: sporoblasts were not highly vacuolated, and the sporophorous vesicle formed before sporogony. In addition to differences in host and geographic location the new species is distinguished from Loma salmonae, the only other species in the genus known from British Columbia, by its internal transcribed spacer (ITS) ribosomal DNA sequence.