482 



COMPARATIVE ANATOMY 



CHAP. 



FIG. 384. Radial-interradial section in the direction of the principal axis through the 

 calyx of Pentacrinus decorus (after P. H. Carpenter), left half radial, right interradial, dia- 

 grammatic. In many respects the figure is obsolete and incorrect. The most noteworthy points 

 are emphasised by special type in the following lettering, sa, Subambulacral plates ; rn, radial 

 nerve trunk (hatched) ; rv, radial pseudoluemal canal (black) ; ra, radial canal of the water vascular 

 system (dotted); d\, brachial coelom ; pi, spongy organ of the blood vascular system ; art, circular 

 canal of the water vascular system ; r>, mouth ; mi (to the right), nerve ring ; ar, blood vascular 

 ring? pseudohsemal ring?; an (to the left), anus; re, rectum; in, plates of the interambulacral 

 areas ; pa, calyx pores ; d, the coelom, traversed by a spongy network ; it, intestinal coils 

 (cut through); gp, axial organ; mu, muscles; <vo, nerve commissure between the axial trunks: 

 bu, basal ; cv, cirrus cMial ; m, cirrus nerve ; ch, chambered sinus, with the centre of the apical 

 nervous system; /-, radial plate; c 1; <.>, first and second costal; di, distichal; si/, syzygial 

 suture ; gr, genital canal ; uni, apical nerve trunk of the arm. 



