ECHINO DERMA TA—S YS TEMA TIG li E VIE W 



307 



Family 4. Melocrinidse. 



Base iiioiiocyclic, 3-5 basals. The basals in contact only with the radials. 

 Interradial areas of the apical capsule with numerous large regularly arranged plates. 

 Plates of the tegmen calycis often small and regular. Orals distinct. Anus sub- 

 central. Mclocri Hits (Fig. 252), Marlacriiius, (T/t/pfocrinus, Steluiiucriiius. 



Family 5. Actinocrinidae. 



Base monocyclic, 3, rarely 4, basals. The first anal plate rests upon the circle of 

 basals ; the first interradials otherwise being in contact only with the circle of 



Fig. 252.— Melocrinus typus, Br. 



//, PinnuUt ; hr, arms ; di, distichals ; 

 c'l, Co, first and second costal ; ;•, radial ; 

 6a, basal ; co, stem ; ir and iil, inter- 

 radial.s. 



Fig. 253.— Batocrinus pyriformis, 

 Shum. (after Meek and Worthen). 

 vk, Ventral capsule ; hr, arms ; p, pin- 

 imlse ; di, distichals ; cj, cj, costals ; 

 /■, radials; ba, basals; co, stem; ir, 

 interradials ; abr, points of insertion 

 of the arms. 



radials. Tegmen calycis usually much ' arched, consisting of numerous firmly 

 connected plates, some of which at least are large, arranged in definite order. The 

 ambulacra of the tegmen calycis with their skeleton hidden, or only visible in forms 

 with flat tegmina. Anus subcentral. Orals usually distinct. C'arjMcriuus, Agarico- 

 crinus, Pericchocrinus, Megistocrimos, Actinocrinus, Tcleiocrimos, Stcganocrinus, 

 Amphoracrinus, Physctocrinus, Strotocrimis, Batocrinus (Fig. 253), Eretmocrinus, 

 Dorycrinus. 



Family 6. Platycrinidse. 



Base monocyclic, 3 basals, which are unc(|ual. Anal and interradial plates not 

 in contact with the basals. The very large radials together with the basals form 



