1885.] NATURAL SCIENCES OF PHTLADELrilTA. 315 



plate. It consists of from three to five pieces, transversely 

 arranged ; the middle one larger, resting upon the sloping upper 

 ends of two first radials ; the outer ones abutting against the 

 large primar} r and smaller succeeding radials. Oral piece large, 

 generally surrounded by proxiraals, which are very prominent. 

 Covering plates frequently exposed upon the surface. Anus 

 subcentral. Column circular or oval. 



G. Hexacrinidje. Base monocyclic. Basals 2 or 3. First 

 anal plate resting on basals, and similar in form to first radials ; 

 other plates arranged as in Platycrinidae. Cabvx with similar 

 armdike extensions. Column circular. 



H. AcROCRiNiD^E. Base monocyclic. Basals 2, separated from 

 the radials by a wide belt of small plates, which are arranged in 

 rings around the basals, and occupy the greater part of the dorsal 

 side. Radials 3X5, increasing in size upwards, all isolated later- 

 ally. Interradials in two rows ; two plates in the lower series, 

 one only in the upper, but the latter larger than the two others. 

 Azygous interradius comparatively much wider, and composed 

 of twice the number of pieces, in addition to the anal plates 

 which form a vertical line. Column circular. 



/. Barrandeocrinid^. Base monocyclic. Basals 3. First 

 anal plate resting on basals ; the interradials upon the sloping 

 upper sides of the first radials. Arms recumbent ; united laterally 

 by their pinnules, and together with these forming a solid integu- 

 ment around the calyx. Column circular, large. 



J. EucALYPTOCRiNiD-a;. Base monocyclic. The dorsal side 

 uniformly composed of 4 basals, 3X5 primary radials, 2X10 sec- 

 ondary radials, 3X5 interradials, and 1X5 inteiaxillaries, there 

 being no anal plates. The ventral side consists of 5 large inter- 

 radials, 5 similar interaxillaries, and 1 small trigonal interbrachial 

 pieces, which form a ring around the dorsal cup, and are suc- 

 ceeded by the summit plates. The summit plates iorm a neck-like 

 prolongation. They consist of 4 large proximals which con- 

 stitute a ring by themselves, of two small proximals, and the 

 oral plate. The latter is bisected and pushed to opposite sides 

 by the anal opening, which is strictly central. The plates of the 

 ventral side are formed into 10 compartments for the reception 

 of ten pairs of arms. Column circular. 



