482 



COMPAEA TIVE ANA TOM Y 



CHAP. 



Fi'.. 384.— Radial-interradial section in tlie direction of tlie principal axis ttirougli tlie 

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

 grammatic. Ill many respects the figure is obsolete and incorrect.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) ; ri\ radial pseudoha-'mal canal (black) ; ra, radial canal of the water vascular 

 system (dotted) ; di, brachial coslom \'pl, spongy organ of the blood vascular system ; an, circular 

 canal of tlie water vascular system ; o, mouth ; tnt, (to the right), nerve ring ; ar, blood ^'ascular 

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

 areas ; jio, calyx pores ; d, the ccelom, traversed by a spongy network ; it, intestinal coils 

 (cut through); rjp, axial organ; -nm, muscles; cm, nerve commissure between the axial trunks; 

 ha, basal ; cv, cirrus canal ; en, cirrus nerve ; cli, chambered sinus, with the centre of the apical 

 nervous system; r, radial plate; c\, c-j,, first and second costal; rfi, distichal; sy, 

 suture ; gv, genital canal ; ar*;, apical nerve trunk of the arm. 



