482 



COMPARATIVE ANATOMY 



CHAP. 



FIG. 3S4. 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 In many respects the figure is obsolete and incorrect.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) ; //, radial pseudoluemal canal (black) ; ra, radial canal of the water vascular 

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

 canal of the water vascular system ; o, mouth ; an (to the right), nerve ring ; av, blood vascular 

 ring? pseudoha?mal 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) ; <jp, axial organ ; inu, muscles ; BOO, nerve commissure between the axial trunks ; 

 bo, basal ; <r, cirrus canal ; en, cirrus nerve ; c/i, chambered sinus, with the centre of the apical 

 nervous system; >-, radial plate; r 1; e.,, first and second costal; <//, distichal; $y, syzygial 

 suture ; </<, genital canal ; am, apical nerve trunk of the arm. 



