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) the shape is visible and then the individual components are developed days later. The size and shape of the operculum bone is dependent on the organism's location. For example, fresh water threespine sticklebacks form a less dense and smaller opercular series in relation to marine threespine sticklebacks. The marine threespine stickleback exhibits a larger and thicker opercular series. This provides evidence that there was an evolutionary change in the operculum bone. The thicker and more dense bone may have been favored due to selective pressures exerted from the threespine stickleback's environment. The development of the operculuar series has changed dramatically