The shells of _Spirula_ (Fig. 44) have been long known, and are scattered in thousands on the shores of New Zealand and other islands in the Pacific Ocean, and they are also found in the Indian and Atlantic Oceans, occasionally drifting on the coast of Devon and Cornwall. Notwithstanding the abundance of the shells, very few specimens of the perfect animal have been captured. The loosely-coiled shell resembles a ram’s horn, and is divided into a number of segments by fine concave partitions, like the shell of _Nautilus_, each one pierced by a slender tube or siphon. It is placed at the hinder end of the body, and is covered with so thin a skin, that a small portion of it appears to be exposed both in front and behind. Absolutely nothing is known of the habits of this very interesting creature, although probably they are somewhat similar to those of other Cephalopods. [Illustration: Fig. 44. The Spirula (_Spirula peronii_). (From the Indian and Pacific Oceans.) 1. Animal: _a_, portions of the shell exposed in front and behind; _b_, the funnel or siphuncle. 2. Side view of shell. 3. Shell in section, to show partitions or septa. ] The _Nautilus_ (Fig. 45), of which several shells (Case 208) and a perfect animal in spirit (black upright case A) are exhibited, is an inhabitant of the Indo-Pacific Ocean, and differs from all other living Cephalopods in being provided with four instead of two gills, and, instead of eight or ten arms with suckers and hooks, has a number of small retractile feelers. The Nautilus occasionally swims, like other members of its class, at the surface of the sea, but mostly crawls about leisurely on its feet at the bottom in search of food, which consists chiefly of small crabs or Mollusca, which it crushes with its strong calcareous parrot-like mandibles. [Illustration: Fig. 45. The Pearly Nautilus (_Nautilus pompilius_). _a_, body; _b_, siphuncle; _c_, eye; _d_, hood; _e_, tentacles; _f_, muscle of attachment to the shell; _g_, siphon. ] The chambered shell is pearly within, and covered with an external calcareous layer. The chambers are connected by a slender tube or siphon, the function of which is not at present thoroughly understood. The septa, or partitions across the shell, indicate periods of growth. When the Nautilus outgrows the capacity of the outer chamber, in which it resides, it constructs a new one of larger size, separating the additional chamber from the preceding one by a transverse partition. A series of Cephalopods preserved in spirit is exhibited in the black upright case at the side of the room. ALPHABETICAL INDEX OF THE FAMILIES AND PRINCIPAL GENERA OF MOLLUSCA EXHIBITED IN THE SHELL GALLERY.