AN'NULA'RIA (Lat. annulus, a small ring) . Ageims of fossil plants found in rocks of De vonian, Carboniferous, and Permian ages, allied to the modern Equisetacea, or Scouring-rushes, and consisting of fluted annulated stems bear ing numerous narrow leaves arranged in whorls at the ring-like joints. .Annularim, for so long a time considered to be plants of a distinct genus, are now' known to be, together with the genera Asterophyllites and Sphenophylhim, merely heteromorphous leaves of the Calamites (q.v.).
or ANNELI'DA (Lat. annu lus, a little ring). A phylum of animals, the an nelids-, comprising a large group of segmented, worm-like forms, mostly included by Linn:eus in his elass Vermes. They have a more or less elongated body, which is always composed of numerous segments. The first of these as sumes, in many, the character of a head, but ill some the head is not clearly set off from the trunk. They have no jointed appendages, but most of them are provided with bristles and hairs, called seta', often in numerous bun dles. which are of use to them in locomotion; Some, which want these, are furnished with suck ers at the extremities, and employ them for this purpose; some remain fixed in one place. Their
bodies are always soft, and without external or internal Ina, some of them form for themselves a calcareous covering by exudation: others form coverings partly by exudation and partly by agglutination. Their blood is gener ally red, but not. from red corpuscles, as in vertebrates; sometimes it is greenish or yellow ish. The circulatory system is well-developed in most annelids, though a few aberrant forms have it greatly reduced or even entirely wanting. It is generally what is called a closed system: that is, the vessels of which it is composed are entirely shut off from with the body cavity. But in the leeches there is no distinction between blood-vessels and body cavity. There are always longitudinal vessels, usually two, sometimes four, time dorsal or lat eral I If which pulsate more or less. These longi tudinal vessels are connected by a. large number of transverse vessels. Some of these near the anterior end of the body are occasionally larger than the rest, and are called "hearts," hut there is no true heart. See ALIMENTARY SYSTEM