Bathylagoides wesethi very low on the underside of the body. The colour is dark brown above with black spots and a black patch around the operculum, which extends halfway up the body. The flanks are silvery-grey and the fins lack pigment. The caudal peduncle is narrow, the caudal fin is short, and the lateral line, which is high on the body, extends into the tail fin. The maximum length to which this fish grows is about . The snubnose blacksmelt is found in deep water in the Pacific Ocean off the western coast of North America. Its range extends from 45°N to
Operculum (fish) over time. The fossil record of the threespine stickleback provide the ancestral shapes of the operculum bone. Overall, the operculum bone became more triangular in shape and thicker in size over time. Genes that are essential in the development of the opercular series is the Eda and Pitx1 genes.These genes are known to be a part of the development and loss of armor plates in gnathostomes. The Endothelin1 pathway is thought to be associated with the development of the operculum bone since it regulates dorsal-ventral patterning of the hyomandibular region. Mutations in Edn1-pathway in zebrafish are known to lead to