SCHUCHERT.] 



ORDINAL CHARACTERS. 



95 



The known protegula, or initial shells, of the Neotiemata and Pro- 

 tremata have been shown to be harmonious, and to diflter from the 

 normal unmodified protegula of the Atremata and Telotremata. The 

 paterina stage in the two last-named orders is followed by the "obo- 

 lella stage" in the highest families of the Atremata (Lingulellidte and 

 Lingulid*), and probably throughout the Telotremata, since it has 

 been observed in a number of Ordovician and Silurian Rhynchonell- 

 acea, Spiriferacea, and recent Terebratulinas.' In the Neotremata 

 and Protremata the paterina stage is not followed by the obolella stage, 

 but usually by holoperipheral growth, except where the pedicle slit 

 remains for a time wholly uninclosed by shell matter." 



In tabulated form the above-presented facts apjiear thus : 



Table of fundamental bracliiopod cJtaracters ordinally arranged. 



It now appears evident that the two great divisions of brachiopods 

 heretofore based on the presence or absence of functional articulation 

 have no phylogenetic significance, and as they "do not appear to have 

 a primary developmental basis in nature, * * * they fail to ex- 

 press the true relationships of the various groups included in thera."^ 



'See papers by Beecher and Clarke, Brooks, Morse, Beecher and Schuchert, and Winchell and 

 Schuchert. 

 2 See Am. Jour. Sci., 3d series, Vol. XLIV, 1891, pp. 150-151. 

 ^Beecher, Am. Jour. Sci., 3d series, Vol. XLI,1891, p. 353 ; also see Vol. XLIV, 1892. 



