1881.] NATtJRAL SCIENCES OP PHILADELPHIA. 267 



basals three ; second primary radials quadrangular and short ; 

 the first anal plate in line with the first radials ; arms heavy, 

 simple, composed of single or double joints. 



c. llelocrimtes : S3mmetry more or less uniformly pentahedral ; 

 calyx large ; basals four or three ; second radials comparatively 

 high and generally hexagonal ; interradials numerous ; anal side 

 but little distinct and its plates not extending to the line of the 

 first radials ; interaxillaries sometimes present ; arms given off 

 laterally ; columnar canal pentalobate and rather large. 



d. Periechocrinites : General symmetry bilateral; calyx very 

 large ; basals four or three ; second radials large, frequently higher 

 than wide ; interradials and interaxillaries numerous ; first anal 

 plate in line with the first radials, succeeded by three plates in the 

 second series; arms branching; column large, and with a wide 

 pentalobate canal. 



e. Actinocrinites : Symmetry slightly bilateral ; calyx large ; 

 basals three ; second primary radials nearly as high as wide, hex- 

 agonal ; higher orders of radials numerous, composed of one series 

 of plates each, which give off the arms alternately from opposite 

 sides ; interradials in two rows ; the first anal plate enclosed be- 

 tween the first radials, supporting only two plates in the second 

 series; interaxillaries generall}' present; arms long, double jointed. 



/. Batocrinites ; symmetry more or less bilateral ; calyx large ; 

 basals three ; second radials short, linear ; higher orders of radials 

 rarely exceeding three, the plates of the last order touching later- 

 ally all around the body, except sometimes over the anal area. 

 Interradials few ; interaxillaries absent ; first anal plate in line 

 with the first radials, second series composed of three plates ; 

 arms short, double jointed. 



These groups are founded upon the construction of the anal 

 area, in connection with the form and arrangement of the radial 

 plates and the arms. A division merely based upon the construc- 

 tion of the anal area, as we have adopted among Platycrinidae, 

 would bring together the Stelidiocrinites and Melocrinites as op- 

 posed to the Agaricocrinites, Periechocrinites and Batocrinites, 

 while the Actinocrinites would occupy a place somewhat between 

 the two. A separation by means of the second primary radials 

 brings into closer proximity Stelidiocrinites and Agaricocrinites, 

 in which those plates are short, linear and quadrangular, against 

 the three other sections in which the}^ are comparatively high and 



