SEA-LILIES AND FEATHER-STARS By AUSTIN H. CLARK (With i6 Plates) CONTENTS p^^E Preface i Number and systematic arrangement of the recent crinoids 2 The interrelationships of the crinoid species 3 Form and structure of the crinoids 4 Viviparous crinoids, and sexual differentiation lo The development of the comatulids lo Regeneration 12 Asymmetry 13 The composition of the crinoid skeleton 15 The distribution of the crinoids 15 The paleontological history of the living crinoids 16 The fossil representatives of the recent crinoid genera 17 The course taken by specialization among the crinoids 18 The occurrence of littoral crinoids 18 The relation of crinoids to temperature 20 Food 22 Locomotion 23 Color 24 The similarity between crinoids and plants 29 Parasites and commensals 34 Commensalism of the crinoids 39 Economic value of the living crinoids 39 Explanation of plates 40 PREFACE Of all the animals living in the sea none have aroused more general interest than the sea-lilies and the feather-stars, the modern repre-sentatives of the Crinoidea. Their delicate, distinctive and beautiful form, their rarity in collections, and the abundance of similar types as fossils in the rocks combined to set the recent crinoids quite apart from the other creatures of the sea and to cause them to be generally regarded as among the greatest curiosities of the animal kingdom. They have usually been considered as the rare, curious and decadent remnants of an interesting animal type once important but now trembling on the verge of extinction, and it is from this melancholy viewpoint that they are discussed in practically all the text-books. Smithsonian Miscellaneous Collections, Vol. 72, No. 7
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