Page:American Seashells (1954).djvu/583

Rh Family ARGON AUTIDAE Genus Argonaut a Linne 1758 Pelagic octopods in which the dorsal arms of the female are broadly- expanded into glandular membranes that secrete and hold a delicate, cal- careous shell for containing the eggs. The males are considerably smaller than the females, do not have a shell, and the third right arm is modified into a detachable copulatory organ which persists separately for a certain length of time in the mantle cavity of the female. Argonaut a argo Linne Common Paper Nautilus Plates ic; 26y Worldwide in warm waters. 4 to 8 inches in length, quite fragile, laterally compressed with a narrow keel, numerous sharp nodules which in the early part of the shell are stained with dark purplish brown. Rest of shell opaque, milky-white. Occasionally washed ashore. A. americana Dall is the same. Argonaut a hians Solander Brown Paper Nautilus Figure gpe, f Worldwide in warm waters. Similar to A. argo, but smaller, much "fatter" with a rapidly broadening keel that bears larger and fewer nodules. Color brownish white with darker stains on the early part of the keel. Uncommonly washed ashore. Family TREMOCTOPODIDAE Genus Tremoctopus Delle Chiaje 1829 Tremoctopus violaceus Delle Chiaje Common Umbrella Octopus Pelagic in warm waters. Worldwide. Total length, including the arms, 3 to 6 feet. Deep purplish red in color. Characterized by the long skin webs between the four dorsal arms, and the two large holes in the body near the base of the third arm and in front of the eyes. The species is gregarious, and is occasionally washed ashore on the east coast of Florida. Family OCTOPODIDAE Genus Octopus Lamarck 1798 There are only five valid species of littoral Octopus so far recorded along the Atlantic Coast. There are a few deep water ones, some of which