116 SYNOPSIS OF AMERICAN FOSSIL BRAOHIOPODA. [bull. 87. 



recognition and establisbniont of certain Driinary characters have 

 resnlted in the discovery of a fundamental structure of general appli- 

 cation for the classification of these organisms. It has for its basis 

 the nature of the pedicle opening and the stages of shell growth. On 

 these characters Beecher has divided the class into four orders — the 

 Atremata, Xeotremata, Protrenuita, and Telotremata.^ 



Hall and Clarke'^ reject Beecher's ordinal terms Atremata and Neo- 

 tremata for the subordinal names Mesokaulia and Daikaulia of Waagen, 

 on the ground of i;)riority, and because the latter terms are " an admira- 

 able expression of the significance of the pedicle i)assage." If some of 

 Waagen's subordinal terms are elevated to ordinal rank and amended 

 by Hall and Clarke, then these terms are no longer Waageu's, but 

 should be credited to Hall and Clarke. Such being the case, the law 

 of priority demands the retention of Beecher's terms, as they do not 

 conflict with those of Waagen but with the secondary definition and 

 rank accorded them by Hall and Clarke. 



On the other hand, Dall claims^ that ^'namesof higher rank than gen- 

 era are not subject to the rule of strict priority, on account of the mutabil- 

 ity of their limits." Again, if Waageu's subordinal terms (and there 

 are seven of them) are to be elevated to ordinal rank — i. e., if the 

 characters upon which they are established are ordinal characters — 

 then all should be elevated alike in rank. Besides the two mentioned 

 above, Hall and Clarke accept also Casteropegmata and Helicopegmata. 

 The latter, however, they retain as suborders, and would do likewise 

 with Kampylopegmata if Gray's term Ancylobrachia of earlier date 

 did not cover the same grouj) of brachiopods; while Gasteropegmata, 

 having certainly no greater value than a superfamily, is elevated to an 

 order. Again, they accept Beecher's Protremata, when Waageu's sub- 

 order Aphaneropegmata could as well be raised to ordinal rank and 

 adapted so as to include the former, since Waagen based the latter 

 upon families having the diagnostic character of the Protremata, 

 namely, the well-developed deltidium. However, a far more important 

 reason why Waageu's terms should not be elevated to ordinal rank 

 and made to displace Beecher's names is that the latter clearly under- 

 stood the value of the different ordinal characters and defined them 

 excellently, which definitions are accepted by Hall and Clarke. He 

 pointed out the most primitive shelled condition in the protegulum, and 

 found this first shell-growth stage in all the important families in the 

 class. He observed that not the mere pedicle slit of the Daikaulia is 

 the ordinal character for ]Sreotrem«> ta, but the way in which growth pro- 

 ceeds to form this derived pedicle slit from the open pedicle notch of 

 primitive forms. He was the first to interpret the true morphologic 



^Development of the Brachipoda, Part I, Am. Jour. Sci., 3^ series, Vol. XLI, 1891 ; Part II, ibid.. 

 Vol. XLIV, 1892. 

 2 Paleontology of Xew York, Vol. VIII, Part II, summary, 1895. 

 3 Trans. Wagner Tree Institute of Science, Phila., Vol. Ill, Part III, 1895, p. 565, Rule XII. 



