Fig. 20. Echinris niiUayis Leske. a young astomous specimeu, 2,5 mm. in 

 diameter, deuuded and dricd; ventral aspect. The stoma is covered 

 all över with the larval envelope, within whicli tlie teeth are seen 

 protruding. The ten pairs of priraary ambulacral plates free from 

 the corona, eucircling the future mouth. The peristome eroded. The 

 buccal membrane with large flakes of calcified tissue. The gills 

 formed. The position of the ambulacral pores heterotropic. 



Fig. 30. Inside view of a part of the peristome seen obliquely, from above aud 

 from the ambulacre IV, so as to show the rotulse, the compasses, the 

 radial muscles, and the epiphyses. The auricles are rising on the 

 ambulacra. 



Fig. 31. Two auricular branches, jpore magnified, to show the sutures marking 

 their bases. 



Fig. 32. Diagrammatic section of the stoma showing the central conical pro- 

 trusion caased by the teeth, the primary pedicels, and the gills. 



Fig. 33. A gill, in dried state. 



Fig. 34. The specimen fig. 29, in dorsal aspect, aproctic. The epistrome, ou 

 the corona spread around the verrucse, is highly developed on the 

 costals and radials of the calyx, but absent on the dorso-central disk, 

 which is thinning off, but still is entire though rounded. 



Fig. 35 — 38. Spinary verrucae breaking through the epistroma. 



