THE HOLOTHURIOIDEA 



231 



Fie- 1. 



Km, 



Fio. IV. 



1. Cttcumnria 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. pentaHts, from which the dorsal region of the body-wall 

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



6. Portion of the calcareous ring of Ornda tenera, Ludw. (After Ludwig.) 



7. Diagrammatic drawing of Khopalculina lageniforniis, Gray. (After Lang.) 



8." Dorsal " view of Psolus nntcmticus (Philippi). (After Tlieel.) 



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



10, Theelia ambulaMx, Bell. 



11. Thyone f*ns (O. F. Mtiller). 



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

 water-vascular canal ; </, cloaca ; g, gonad ; f/.d, genital duct ; g.p, genital pore ; i, 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.r, mesenterial blood-vessel ; p, podium ; 

 j>.r, 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. 



