SPIRIMA., a genus of polythamous, decapodous, dibranchiate cephalopods, com prising three species, and constituting prof. Owen's family, spirnlida, in which the internal skeleton is in the form of a nacreous, discoidal shell, the whorls of which are not in contact with one another, and which are divided into a series of chambers by partitions pierced by a ventral tube or siphuncle. The animal has minute lateral fins, and there are six rows of small suckers on the arms (see CEPHALOPODA). The three species constituting the family, or the genus, which in this case is the same, are, as designated by prof. Owen, spirula, peronii, S. australis, and S. reticulate, and are formed from the nautilius spirula of Limmus. The shell of one or other of these species is not tinfrequently found on the coasts of Ireland, Cornwall, and Devon. It is commonly known as the post-horn, and is similar in structure to that of the nautilus, but is lodged in the posterior part of the animal, and is therefore internal, whereas the shell of the nautilus is external. It corresponds to the phragmacone of the belemnite (q.v.). The
thells are found in great numbers in certain localities, but the animal has seldom been taken whole. In its internal anatomy it is a true dibranchiate, having two branchiat And an ink-bag. It has the peculiar feature that the hinder end of the body acts as a kuctorial disk for fastening itself to foreign bodies. The beaks are not calcified, and the retractor of the funnel spring from the inner surface of the last chamber i)f the shell, as in the nautilus. This chamber also lodges the hinder termination of the liver (Owen). For a long time only imperfect specimens, or portions of the animal, were obtained, and there was much discussion among naturalists as to its proper place, until one was obtained in a perfect state by Mr. Percy Earle on the coast of New Zea land, where the shells are found in great abundance.