593.91 337 



YII 



Wachsmuth and Springer's Classification of 



Crinoids ^ 



A LITTLE less than a year ago was published the largest book 

 that has ever been issued all at one time on a crinoid sub- 

 ject. It represents a portion of the final results of over thirty years 

 work by the late Charles Wachsmuth, in collaboration for the last 

 twenty years with Frank Springer. These authors have long been 

 recognised as the leading authorities on Palaeozoic crinoids, a position 

 won chiefly by their most valuable " Revision of the Palaeocrinoidea," 

 published by the Philadelphia Academy of Natural Science. That 

 work, however, was but a paving the way for a greater enterprise, 

 namely, the monographing of all the Palaeozoic crinoids of North 

 America. This task can never be accomplished by them, though 

 it is to be hoped that the survivor may find opportunity to give us 

 the fruits of his knowledge in the remaining branches of the subject. 

 The present volumes are occupied mainly with the systematic account 

 of the North American representatives of those crinoids known as 

 Camerata or ' vaulted ' crinoids ; but they contain also introductory 

 and morphological parts, dealing with the Crinoidea as a whole. 

 The points raised are so many, often so novel, and the treatment of 

 them so important, that it would be impossible to discuss them 

 adequately in a single article. On the present occasion I shall 

 merely attempt a critical account of the authors' classification of the 

 Crinoidea. 



A crinoid reduced to its simplest elements consists of three 

 principal portions — (i.) a theca or test enclosing the viscera ; (ii.) five 

 arms stretching upwards or outwards from the theca, sometimes single, 

 sometimes branching ; (iii.) a stem stretching downwards from the 

 theca and attaching it to the sea-floor. The theca and arms together 

 are called the ' crown ' ; that part of the theca below the origins of 

 the free arms is called the ' dorsal cup ' ; while the ventral part 

 above the origins of the arms, serving as cover to the cup, is known 

 as the ' tegmen.' All these parts are supported by plates or ossicles 

 of crystalline carbonate of lime, deposited in the meshes of the lower 

 layers of the integument. In many cases the skeletal tissue or 



^ The North American Crinoidea Camerata. By Charles Wachsmuth and Frank 

 Springer. Mem. Mus. Comp. Zool. Harvard, vols. xx. and xxi., 837 pp. and 83 pis. 

 Cambridge, U.S.A., May 1897. 



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