^S. tenuis.^ This curious animal is long and slender, and so transparent that its internal organs are clearly visible. Around the mouth are a circular tube and a wreath of twelve branching tentacles. There are no ambulacra. Little spots scattered irregularly over the surface show, when highly magnified, small warts, each one of which has a calcareous projection shaped like a little anchor. By means of these anchors and by the contractions of its body the animal moves through the mud or sand in which it lives, near low-water mark. The sand is collected into rings at the oral end and pushed downward until the whole animal is inclosed in a sand-tube. When empty /Synapta/ is white and transparent, and the digestive canal may be seen wound in a spiral throughout its length; but when gorged with food, sand, pebbles, and shells can be distinctly seen filling the food-canal, and the body then has a dark-gray color. /Synapta/ grows to a length of eighteen inches or more, but is constantly breaking pieces off its posterior end by muscular contractions. When kept in confinement it soon commences to constrict its body at various points, and after a few hours there is nothing left but a mass of fragments. It is viviparous, that is, it carries its young in the body-cavity; the eggs are hatched, and the young approach maturity before they are expelled. This species ranges from Cape Cod to North Carolina, and can be found in the upper part of its burrows when the tide is out. ^S. roseola.^ This species occurs in the same localities as /S. tenuis/, and differs from it mainly in color, which is pale red, due to minute red spots scattered through the skin. ^S. rotifera.^ A species found in Florida. It is light purplish in color, and has eight or ten branches on each of the twelve tentacles. In this species the spicules of lime in the skin are shaped like wheels instead of anchors. GENUS ^Caudina^ ^C. arenata.^ About four inches long and tapers to the ends; the posterior end sometimes narrowed to a long, slender, tail-like extremity; tentacles around the mouth resemble cloves. It lives in sand and may be found on the New England coast, washed ashore after a storm. [pg234] Class =CRINOIDEA= Genera ^Pentacrinus^ ^Comatula^ CLASS =CRINOIDEA= FEATHER-STARS AND SEA-LILIES [Illustration: The feather-star (/Antedon/), illustrating the /Comatula/ form of crinoid.]