Zöology; a textbook for colleges and universities . e Pelmatozoa in-clude the cystoids,blastoids, and cri-noids, but only thelast of these divisionsis living today. Theother two disappearedbefore the end of Pa-Iseozoic time, but wereimportant groups intheir day. The Pel-matozoa are fixed,usually with a distinctstalk, on the aboralsurface, and conse-quently the mouthis directed to thisstatement are found,however, in the adultsof many crinoids, IGSI which are wholly free, and might easily be confusedwith starfishes. The word crinoid means like a lilyand has been given because o
Zöology; a textbook for colleges and universities . e Pelmatozoa in-clude the cystoids,blastoids, and cri-noids, but only thelast of these divisionsis living today. Theother two disappearedbefore the end of Pa-Iseozoic time, but wereimportant groups intheir day. The Pel-matozoa are fixed,usually with a distinctstalk, on the aboralsurface, and conse-quently the mouthis directed to thisstatement are found,however, in the adultsof many crinoids, IGSI which are wholly free, and might easily be confusedwith starfishes. The word crinoid means like a lilyand has been given because of the long-stalked forms,with the so-called calyx and feathery arms at the sum-mit, resembling flowering plants. The crinoids weredominant during the Palaeozoic, producing innumerablegenera and species, often of large size and complex wonderful slab of fossil crinoids (Scyphocrinites) maybe seen in the United States National Museum. Theseexisted during a period when much of the interior ofNorth America, east of the Rocky Mountains, was cov-. From Perriers Traite de ZoologieIsocrinus (or Pentacrinus) asteria. Crinoids orsea lilies 222 ZOOLOGY ered by a shallow sea, an American Mediterranean. Inthese waters crinoids existed in vast numbers, and theirremains may be found in the rocks over a large part ofthe country. When this sea was drained, during theMesozoic, the crinoids mostly died out, leaving com-paratively few representatives. In more modern timesmany genera and species of crinoids have come into ex-istence, but they mostly show little resemblance to thoseof remote antiquity, and there is no reason to supposethat the group will ever again recover its ancient glory. starfish 4. The Asterozoa, or star animals (Greek, aster, a star, from which our English word is little modified), in-clude the starfishes and brittle stars. There are veryimportant differences between these groups, althoughboth have the starlike form, with arms extending froma central disk. In the Aster
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