THE HOLOTHURIOIDEA 



231 



KfTL 



FlO. IV. 



1. Cucumarla pentactes (Linn.), opened along the right of the median dorsal line ; the 

 right respiratory tree has been cut short. 2. Spicule ; 3. Oral view ; and 4. Left side view 

 of the same. 



5. Inner view of a retracted C. pcntactes, from which the dorsal region of the body-wall 

 has been removed, and the viscera extracted, to show the action of the retractor muscles. 



0. Portion of the calcareous ring of Oraila tenera, Liidw. (After Ludwig.) 



7. Diagrammatic drawing of Rhopalodina lageniformis, Gray. (After Lang.) 



8." Dorsal " view of Psolas antarctinis (Philippi). (After Theel.) 



9. Left side view of Sphaerothuria Mtentaculata, Ludw. (After Ludwig.) 



10. Theelia ambulatrix, Bell. 



11. Thyone fiisus (O. F. Mitller). 



a, anus ; o. v, anti-mesenterial blood-vessel ; b.w, body- wall ; ca.r, calcareous ring ; c.c, circular 

 water-vascular canal ; cl, cloaca ; g, gonad ; g.d, genital duct ; g.p, genital pore ; t, intestine ; 

 i.p, interradial piece ; l.d.r, left dorsal radius ; l.r.t, left respiratory tree ; l.v.r, left ventral 

 radius ; m, mouth ; m.r, median ventral radius ; m.v, mesenterial blood-vessel ; p, podium ; 

 p.v, polian vesicle ; r.c, radial canal ; r.d.r, right dorsal radius ; r.m retractor muscle ; r.p, 

 radial piece ; r.r.t, right respiratory tree ; s. creeping sole ; s.c, stone canal ; t, tentacle. 



