A SYNOPSIS OF AMERICAN EARLY TERTIARY 

 CHEILOSTOME BRYOZOA. 



By Ferdinand Canu, 



Of Versailles, France. 



AND 



Ray S. Bassler, 

 Of Washington, District of ColuniMa. 



PRINCIPLES OF CLASSIFICATION. 



The principles of classification of the cheilostome bryozoa are 

 still imperfect in spite of the quite extended researches of several 

 students. Formerly the classification was based on pm^ely zoarial 

 features, but in the latter half of the nineteenth century the zocecial 

 characters were more closely studied, especially by D'Orbigny, Smitt, 

 and Hincks. The latter author considered especially the form of 

 the aperture; in other words, only the hydrostatic system. In 1888 

 and again in 1903 J. Jullien established a systematic set of charac- 

 ters for consideration. These are as follows in diminishing order 

 of importance. 



Essential characters. — (1) General morphology (order); (2) form 

 of the frontal wall (suborder) ; (3) form of the aperture and of the 

 operculum (family) ; (4) presence of carclelles, occurrence of lyrula 

 and finally ovicells and radicels. 



Secondary characters {specific). — Frontal punctations, avicula^ria, 

 and vibracula. 



In 1900 Canu wrote that every family ought to be based on an 

 anatomical peculiarity, common to all its members and fixed in an 

 uninterrupted series of descendance. He established the genera 

 according to the variations of this anatomical peculiarity and accord- 

 ing to the divergence in its evolutionary characters. This was a 

 perfection of Jullien's ideas, but the partial application made by 

 Waters to the opercula and the avicularian mandibles did not appear 

 always to lead to uniform results or to the establishment of very 

 natural genera. 



We believe that other principles are better. In the bryozoa as 

 in other living beings the form is only the result of a function; 



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