MONOGRAPH OF THE EXISTING CBINOIDS. 105 



Syzygy. — (1) An immovable articulation formed exclusively of ligament fibc'-s; in 

 the comatulids the apposed faces arc marked with numerous fine radiating 

 ridges; externally the syzygy appears as a narrow usually whitish lino win- 

 ning across the arm at right angles to the longitudinal axis (see figs. 2, p. 61, 

 6, p. 63, 30, 34, p. 71, and 35, p. 73, and p. 113). 



(2) This term is often used to denote a pair of ossicles united by syzygy, 

 that is, a syzygial pair. 



(3) Pourtales has used this word as the equivalent of intersyzygial inter- 

 val, in Minckert's sense; that is, to denote all the brachials between two adja- 

 cent syzygies. 



T. 



Tegmcn or legmen calycis. — See Dislc. 



Terminal axillary. — In the comasterids, the terminal orachial of an ungrooved arm, 

 when that brachial bears two pmmdes instead of one pumule and another 

 brachial as usual (see fig. 47, p. 81). 



Terminal claw.— The conical, sharp pomted, more or less curved ossicle which forms 

 the termination of a cu-rus (see figs. 4, p. 63, 314-318, p. 273, and pp. 276-278). 



Terminal comh. — See Comh. 



Terminal pinnules.— The pmnules of the extreme arm tip (see figs. 46, 47, p. 81). 



Terminal stem plate. — The Dorsocentral. 



Tertibrachs (IIIBr). — The ossicles composmg a division series or an arm arising 

 from a TIBr (distichal) axillary; the palmars. 



Tetrabraclts (IVBr).— The ossicles composing a division series or an arm arising 

 from a IIIBr (pabnar) axillary; tlie fii'st post-palmars. 



Topmost columnal. — See Proximal columnal. 



Transition segment.— The segment upon which the transition between the longer 

 smooth and the shorter spmous (distal) cu-rus segments takes place; the transi- 

 tion segment usually resembles the segments precedmg in its proxmial two- 

 thu-ds, and the segments succeedmg m its distal thu-d; it is commonly darker 

 in color than any of the other cu-rus segments (see figs. 4, p. 63, 363-367, p. 297, 

 and pp. 290-292). 



Transverse ridge.— {1) On the jomt faces of a muscular articulation, the strong 

 ridge crossmg the jomt face just dorsal to the central canal and separating the 

 large single dorsal ligament fossa from the pau-ed mterarticular ligament 

 fossa?- it'serves as the fulcrum upon which the motion at the articulation is 

 accommodated (see figs. 9-11, p. 65, 31, 32, p. 71, and 431, p. 349, and p. 114). 

 (2) On the dorsal surface of the cirrus segments, a serrate ridge, some- 

 times more or less crescentic, which traverses the segments at right angles to 

 the longitudinal axis; it is commoidy central or subterminal m position; trans- 

 verse ridges on the cirrus segments are only developed in a few genera (see 

 figs. 345,"?. 289, 349, 352, p. 291, and 353, p. 293, and p. 109). 

 Triangular pinnules.^ee Prismatic pinnules. 



79146°— Bull. 82—15 8 



