1 84 ECHINODERMATA— PELMATOZOA phylum iv 



most part, as subordinate to them, the orders proposed by Wachsmuth and 

 Springer. The divisions established by Wachsmnth and Springer have been 

 adopted as the basis of the following systematic arrangement, substituting, 

 however, for their Articulata the preferable name Flexibilia, proposed by von 

 Zittel in 1895, and now adopted by Springer in his forthcoming monograph 

 of that group ; also retaining the name Articulata in the sense of Miller and 

 Miiller for a fourth division, including the Eecent and most of the Mesozoic 

 Crinoids. 



Within the last few years, also, the terminology has been amended in 

 several important resj^ects ; and conformably to the usage of the leading 

 English and American authorities, certain of these changes have been adopted 

 in the present edition. An explanatory note on the use of terms is therefore 

 given at this place, in order to facilitate reference, and to exhibit the corre- 

 spondence between the older terminology and the new. 



The only abbreviations employed in the text are the following : — 



IB = Infrabasal. Br = Brachial. 



i?= Basal. /i?r= Primibracli or costal. 



i2^=Radianal. //5r = Secuiidibracli or disticlial. 

 a; = First or special anal. •ii?r=Iuterbracliial. 



^ = Radial. .4m& = Ainbulacrals. 



In addition to these the following are used in the figures, but are printed 

 in small letters : — 



^= Calyx. = Orals. 



A = Arras. IH = Interradials. 



St = Stcm. Z)isi =:Disticlials. 



Explanation of Terms. 



Crow7i = Criuoid minus the stem. 



Oahjx = Crinoid skeleton minus the stem and free arms. 



Dorsal ctq) = AW parts of the calyx below the origin of the free arms. 



Tegme7i = Th.a,t part of the calyx lying above the origin of the free arms, and embracing 

 the disk ambulacra, the mouth, and the aniis. Includes the terms ventral disk, vault, 

 dome, swmmit, etc. 



^«se = That part of the dorsal cup lying next to the column. It may be composed of one 

 ring of plates (monocyclic), or of two rings (dicyclic), which are distinguished as basals and 

 infrahasals. The basals adjoin the radials and alternate with them, being interradial in 

 position. The infrahasals, when ju'esent, form the proximal ring, and are radially disposed. 



Radials = T\ie circlet formed by the first plate in each of the rays; or, the radially 

 situated circlet of plates above the basals, and this ring only. In some of the earlier Crinoids 

 one or more of the radials appear as if transversely bisected, due to the presence of a 

 radiaiial or inferradials. 



Brachials = AW plates beyond the radials in radial succession. They are called fixed 

 brachials so far as tliey take part in the calyx ; /ree brachials or nrm-platfs when they do 

 not. The brachials forming the first circlet above the radials, whether free or fixed, are 

 called primihrachs or costals ; those of the second order secundihrachs or distichals ; those of 

 the third order tertihrachs or palmars; and so on for succeeding orders of brachials, to which 

 formerly the name post-palmars was applied. 



Interradials = AW plates occupying the spaces between the rays proper, whether they 

 belong to the dorsal cup or the ventral disk. Those of the dorsal cup, which are inter- 

 posed between the brachials, are distinguisluid as intcrhrachials, and those of the tegmen, 

 which lie between the ambulacra, as interamlulacrals. 



Eadianal = A plate disturbing the bilateral symmetry of the cup, located primitively 

 directly below the right posterior radial, and in later genera obliquely to the. left of it. 



yi7trtZs = Interradials of the posterior side, forming the base of the anal structures. The 

 special or first anal plate (now usually designated x), when present, invariably rests upon 

 the truncated upper face of the posterior basal and between the radials. Higher anal plates 



