The Open-bills, or Shell Storks (Anastomus), are among the smallest of the group, being only twenty-eight or thirty inches in length. They are known at once by the fact that the bill gapes widely toward the tip, leaving, as suggested by the name, an open space of considerable extent in the terminal half of the bill. It was supposed that this resulted from wearing away in the process of securing their food, but it has been asserted on good authority that the young birds exhibit the same feature, and hence it is structural. They live on shell-fish, such as fresh-water mollusks, whence of course their second name. Of the two species known, the Indian (A. oscitans) is pure white both above and below, with the exception of the wings and their primary coverts, and the feathers of the tail, which are black with purple and green reflections. The African species (A. lamelligerus) is largely black with metallic green and purple reflections, the feathers of the crown, throat, breast, and under parts with narrow horny tips. The Open-bills nest among the reeds in marshes or occasionally in trees, returning year after year to their old nesting sites.