172 SPOLTA ZEYLAXTCA. 



{a) With anal teeth. 



Argiodia. 



(b) Without anal teeth, 



(a) Pedicels on trivium. Papillae on bivium. 

 Halodeima. 



(^) True pedicels absent. Papillse scattered 

 all over the body. Generally on 

 eminences. 

 Thymiosicya. 



Explanation of Plate XXVI. 



Fig. 1. — Siinplest f orin of calcareous ring consisting of five radials 

 and five inter-radials. i.r. = inter-radial ; r. = radial. 



Fig. 2. — Simple form having an anterior notch in each radial, 

 for the insertion of the radial muscle. 



Fig. 3. ^Simple form bearing ampullary notches : two complete 

 notches and two half notches for each radial, and two half notches 

 for each inter -radial, a. n. — ampullary notch. 



Fig. 4. — Calcareovis ring of Actinopyga miliaris (Quoy & 

 Gaimard). 



Fig. 5. — Calcareous ring of Bohadschia vitiensis (Semper). 



Fig. 6. — Calcareous ring of Argiodia maculata (Brandt). 



Fig. 7. — Calcareous ring of Thymiosicya hamata (Pearson). 



Fig. 8. — Calcareous ring of Halodeima vagdbunda (Selenka). 



