704 A CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



fossil types." Ulrich and Ruedemann considered that the graptolites were more 

 closely related to the Bryozoans because of the character of the sicula, the mode 

 of budding from the sicula, the bilateral symmetrical thecae, and the similar 

 habitus of the two groups. Recently R. Kozlowski (1948), in studying excellently 

 preserved material from Lower Ordovician cherts in Poland, has concluded that 

 the graptolites are closely related to the living Pterobranch Rhahdopleura of the 

 phylum Hemichordata. 



The fossil Medusae, which usually possess only a slight resemblance to living 

 medusae, have been described in an important monograph by C. D. Walcott 

 (1898). During the second half of the nineteenth century many species were 

 figured and discussed by Beyrich, Haeckel, Ammon, and Nothorst. 



E chinodermata : The accumulated information of 1850 concerning the mor- 

 phology and classification of the phylum E chinodermata had resulted from in- 

 vestigations carried on in both Europe and North America. The Crinoidea were 

 established as an independent group by J. S. Miller in 1821, the Blastoidea by 

 Fleming in 1828 and the Cystoidea by von Buch in 1845. In 1848 Leuckart 

 combined these under the class name Pelmatazoa and placed it along with other 

 echinodern groups in the phylum Echinodermata. Important monographs by 

 Goldfuss and Munster in 1826, Johannes Miiller in 1841, Vaughn Thompson in 

 1836, Edward Forbes in 1848, and d'Orbigny in 1840-1860 emphasized the mor- 

 phological details of genera and families along with the description and illus- 

 tration of new species with attempts at broad classifications. From 1850 to 1950 

 a very extensive literature accumulated concerning the morphology and classi- 

 fication of echinoderms and the relationships of genera to their stratigraphic 

 succession. 



The earliest classifications of the Pelmatazoa were not founded on morpho- 

 logical principles, and many greatly differing forms were combined and placed 

 in the same group. The Blastoids and Cystoids were placed by those immediately 

 following J. S. Miller as a subordinate group under the Crinoids. Miller had 

 divided the Crinoids into four groups, largely on the number and arrangement 

 of the plates in the dorsal cup. Most investigators following Johannes Miiller 

 considered that all Paleozoic forms were distinct from later ones and it was not 

 until the publication of Carpenter's work in the "Challenger" reports in 1884 

 on the stalked Crinoids that the morphological relations between the Mesozoic 

 and Paleozoic forms became known. He held that the Paleozoic Crinoids dif- 

 fered from those of later age in the character of their irregular symmetry. 

 Many new species and genera of Crinoids and Cystoids from Bohemia were de- 

 scribed by J. Barrande between 1877 and 1899. In 1845 von Buch gave the 

 Cystoidea equal rank with the Blastoidea and Crinoidea. Ferdinand Roemer 

 in 1855 published an important memoir on the Cystoidea and Blastoidea and 

 divided the former into three groups. Neumayr considered the Cystoidea, Blas- 

 toidea, and Crinoidea independent classes and believed that the two last were 

 derived from the Cystoidea. 



During the fourth quarter of the nineteenth century the Pelmatazoa were 

 the subject of intensive investigation by North American paleontologists. Among 

 the more noteworthy were F. B. Meek, A. H. Worthen, E. Billings, James Hall, 

 Charles Wachsmuth, and Frank Springer. Under the auspices of the Geological 

 Survey of Canada Billings, in 1869 and 1870, published contributions on the 



