314 PROCEEDINGS OP TIIE ACADEMY OF [1885. 



anal plates, which extend to the anal aperture. Arms single- 

 jointed ; pinnules strong. Anus subcentral. Column circular 

 or angular. 



B. RuoDocRiNiDiE. Base dicyclic. First radials separated 

 from one another by the first interraclials, with which they form 

 a ring of ten plates around the basals. Interradial areas com- 

 posed of well-formed plates, definitely arranged; azygous side 

 scarcely distinct. The interradials in all earlier forms along the 

 ventral side are arranged like those of the Reteocrinidre, and the 

 proximals are probably unrepresented ; but in the later ones prox- 

 imals are well developed. Anus subcentral. Column circular 

 or obtusely pentangular. 



G. G-i-YPTASTELiiDiE. Base dicyclic. First anal plate resting 

 on the basals, but the first interradials not touching them. Suc- 

 ceeding interradials arranged as in the Rhodocrinidae. Those 

 upon the ventral surface are sometimes composed of larger plates 

 than in the preceding groups. Anus subcentral. Oral piece and 

 proximals well represented. Column circular or pentangular. 



D. Melocrinid^e. B.ise monocyclic. Basals 3 to 5. Neither 

 anal nor interradial plates touching the basals; the latter in con- 

 tact with radials only. Interradial areas composed of numerous 

 plates; those upon the dorsal side large, regularly arranged, 

 those along the ventral surface frequently small and irregular. 

 Oral plate generally surrounded by proximals. Anus subcentral. 

 Column circular, rarely angular. 



E. AcTiNocRiNiDiE. Base monocyclic. Basals 3, rarely 4. 

 First anal plate resting on basals, the first -interradials upon the 

 sloping sides of the first radials. The interradials together with 

 the interax diaries, anal plates and proximals, form a solid vault 

 over the disk, rarely exposing any of the covering plates. Anus 

 subcentral. Column circular. 



jF. Plat Yi rim im;. Base monoc3 r clic. Basals unequal. Neither 

 anal nor interradial plates touching the basals. First radials 

 extremely large, forming with the basals almost the whole dorsal 

 aspect of the calyx. Second radial small and short, and likewise 

 the higher orders of radials, which in place of being connected 

 by interradials, are formed into lateral branches or free append- 

 ages. Interraclials three at least, generally more; all located 

 more or less ventrally. The lower range contains no special anal 



