TERMINOLOGY IO, 



TERMINOLOGY 



The terms employed in this work differ in some particulars from those 

 used by Wachsmuth and Springer in the Crinoidea Camerata memoir. The 

 difference is chiefly in regard to the plates of the brachial series succeeding the 

 radials. For these I have heretofore adopted and shall continue to use the 

 nomenclature and symbols proposed by Bather in Lankester's Treatise on 

 Zoology, Pt. Ill, p. 143, and previous papers, as being the most philosophical 

 and accurate, and also the logical consequence of our own researches. This 

 conclusion was stated in my memoir on Uintacrinus, 1 and I will restate the 

 reasons for it. When in 1881 and 1885" we showed that the arms funda- 

 mentally begin with the second plate of the ray — i. e., that all plates of the ray 

 above the radial circlet, whether free or not, are brachials — it logically followed 

 that they ought to be designated according to their numerical succession; and 

 we in fact proposed to use the terms " primary," " secondary " and " tertiary " 

 brachials, etc. Upon conference with P. H. Carpenter, who thought those 

 terms too long and cumbrous, we agreed to adhere to the Miillerian " costals," 

 " distichals " and " palmars," as proposed by him. 3 In the Camerata mono- 

 graph 4 we retained, in an explanatory sense, the alternative terms " primary 

 brachials," " secondary brachials," " tertiary brachials," followed by " brachials 

 of the fourth order," and so on, and employed for them the symbols I, II, III, 

 IV, etc. Bather's invention of the terms " primibrachs," " secundibrachs," etc., 

 and the other terms naturally accompanying them, with their convenient sym- 

 bols, was a solution of the difficulty, and furnished a terminology for these 

 parts consistent, convenient in use, and easily remembered; and I have em- 

 ployed them ever since, not without, however, an occasional lingering regret 

 for the strong and terse designations of Muller. 



Some of the innovations agreed upon by the authors above cited are of 

 questionable advantage. This is notably the case with the old familiar terms 

 " interradials " and " interbrachials," the former meaning plates between the 

 rays, and the latter plates between their divisions. In order to make the de- 

 scriptive term conform to the current morphological concept (it having been 

 decided that all plates of the ray above the radial circlet belong fundamentally 

 to the arms and are therefore all " brachials "), the term " interbrachials " was 

 shifted so as to apply to that portion of the plates between the rays which are 

 above the radial circlet. This leaves no appropriate or special term for those 



'Mem. Mus. Comp. Zoology, Harvard, vol. 25, no. I, 1901, p. 41. 



2 Revision of the Palaeocrinoidea, pt. 2, p. 10; ibid, pt. 3, p. 12. 



3 Carpenter, P. H., Ann. and Mag. Nat. Hist. (6), vol. 6, 1890, pp. 11-18; Wachsmuth and Springer, 

 Proc. Acad. Nat. Sci., Philadelphia, vol. 42, Oct., 1890, pp. 374-375. 



* Mem. Mus. Comp. Zoology, Harvard, vol. 20, 1897, pp. 73-75. 



