SCHUCHERT.] 



ORDINAL CHARACTERS. 



95 



The known jirotegula, or initial shells, of the Neotiemata and Pro 

 treniata have been shown to be harmonions, and to difler from the 

 normal nnmodilied protegula of the Atremata and Tclotrciuata. The 

 pateriua staj^e in the two last-named orders is followed by the "obo- 

 lella sta,i»e'' in the highest families of the Atremata (Linonlellida' and 

 Lingnlida'), and probably thronghont the Telotrcmata, since it has 

 been observed in a number of Onlovieian and Silurian lihynchonell- 

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

 and Protremata the i)aterina stage is not followed by the obolella stage, 

 but usually bj^ hoI()i)erii)heral growth, except where the jjcdicle slit 

 remains lor a time wholly uuiuclosed by shell matter." 



In tabulated form the above-presented facts appear thus: 



Tabic of fuiidavtrntal hracJiiopod characters or(H)ialhi arranged. 



It now appears evident that the two great divisions of brachiopods 

 heretofore based on the presence or absence of functional articulation 

 have no phylogenctic 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 them."' 



'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. 



