The structure of the pituitary in fish, apart from the lungfish, is generally different from that in other animals. In general, the intermediate lobe tends to be well developed, and may equal the remainder of the anterior pituitary in size. The posterior lobe typically forms a sheet of tissue at the base of the pituitary stalk, and in most cases sends irregular finger-like projection into the tissue of the anterior pituitary, which lies directly beneath it. The anterior pituitary is typically divided into two regions, a more anterior "rostral" portion and a posterior "proximal" portion, but the boundary between the two is often not clearly marked. In elasmobranchs there is an additional, "ventral lobe" beneath the anterior pituitary proper.