REVIEWS. 



The Crinoidea Flexibilia. By Frank Springer. 4to, vi + 

 486 pp., 79 plates. Smithsonian Institution, Publication 2,501. 

 Washington, 1920. 



OINCE the publication of the monograph on the Crinoidea 

 '^ Camerata and the death of its senior author, Charles Wachsmuth, 

 in 1896, Mr. Springer has devoted the leisure of a busy life to the 

 study of another Order of the Crinoidea — the Flexibilia. The 

 result is presented in these handsome volumes, for which gratitude 

 on our part is more becoming than praise. This monograph 

 differs from its jiredecessor w that it treats of all the known 

 species from whatever part of the world they come. To attain 

 this comprehensiveness Mr. Springer has drawn upon an unusually 

 large number of public and private collections, and by employing 

 collectors in the field has added mach new and interesting material 

 to his own collection, housed in the United States National Museum. 

 Those individuals and institutions who have confided their treasures, 

 and in some cases their notes, to Mr. Spruiger for publication must 

 feel proud that they have contributed to so magnificent an edifice, 

 and must realize how far more they have advanced science than they 

 could have done by impatiently forestalling his labours. Doubtless 

 they knew that they were in safe hands. Mr. Spriager has, in fact, 

 given them the fullest credit, and, as type-specimens of species 

 newly described from other countries, he has selected, where possible, 

 specimens in the respective national museums. 



All this exploration was necessary because the Flexibilia are the 

 rarest of crinoids. Specimens were almost unknown to the early 

 writers, even down to Johannes Miiller, and when they became 

 knowTi their nature was at first little understood. The reason, 

 apart from rarity, is that the Order is a peculiar one. While some 

 genera, such as Sagenocrinus, superficially resemble the Camerata, 

 others, such as Lecanocrinus, can be distinguished only with difficulty 

 from the Inadunata. The former resemblance, such as it is, is due 

 to convergence ; the latter proves, as suggested in 1900, to be 

 the expression of relationship, for Lecanocrinus is connected, 

 through Protaxocrinus and Cupidocrinus of the Lower Trenton, 

 with the Dendrocrinidae. Moreover, the diagnostic characters of 

 the Order are obscure ; the finely plated skin, by which the arms 

 in some genera were loosely joined, has generally disappeared 

 from the fossils ; the open mouth is invisible in all but the rarest 

 specimens ; the loose union of the skeletal elements is a feature 

 more readily appreciated by the experienced eye than described 

 in good set terms. 



Here, however, we cannot pause to discuss those questions of 

 anatomy and affinity so admirably dealt with by Mr. Springer. 

 The most useful employment of allotted space will be to give a 



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