Pacific bonito head. The caudal peduncle is slender, and the body entirely scaled. It has no teeth on the vomer. It has a small keel on either side of the median keel on the sides of the caudal peduncle, and six to eight finlets on the dorsal and ventral surfaces of the caudal peduncle. The maximum length is about 40 inches and weight 25 pounds. It is found anywhere from inshore to about 100 miles offshore from northern Vancouver Island to Mexico, though it is not normally found north of Point Conception. It usually travels in schools. Fish and squid are its
Operculum (gastropod) to push into the substrate in a leaping form of locomotion. Virtually all pulmonate snails are inoperculate, i.e. they do not have an operculum, with the exception of the Amphiboloidea. However, some terrestrial pulmonate species are capable of secreting an epiphragm, a temporary structure that can in some cases serve some of the same functions as an operculum. The epiphragm may be distinguished from the true operculum by its homogeneity and want of growth marks. In ammonites (extinct shelled cephalopods), a calcareous structure known as the aptychus (plural aptychi) existed. When these were first described they were thought to be