1879.] NATURAL SCIENCES OF PHILADELPHIA. 321 



A. Typical form. 



The crinoids of this type resemble in general form a tree with 

 many branches and branchlets. Calyx small, cyathiform, un- 

 sj-mmetrical. 



Underbasals five, slightly protuberant. Basals five, three of 

 them equal, the other two of somewhat different form, due to their 

 abutting against the anal plates. Radials large, articulating sur- 

 face concave, occupying more than three-fourths of the width of 

 the plate. Brachials less than one-half the size of the radials, 

 wider than high, their number varying in the rays from two to 

 five. 



Each ray is composed of two main arms from which, through? 

 out their entire length, spring two rows of branches, given off on 

 alternate sides from every second or third joint, and which ex- 

 tend to the very top of the specimen. The secondary arms branch 

 again, throwing off branchlets right and left, which themselves 

 ramify, thus producing branches of a third and fourth order. The 

 main arms are heavy, almost as wide at the base as the brachials, 

 and decreasing in size very gradually toward the tips. The sec- 

 ondary branches are about two-thirds the size of the former, and 

 those of the succeeding orders are slender, short, not reaching to 

 the top of the specimen. The plates of arms and branches of cor- 

 responding position, throughout the specimen, are of equal width 

 and height, those of the branches being relatively shorter. Ar- 

 ticulating face of arm joints and brachials circular. 



Anal plates two, arranged as in Homocrinus ; the lower one 

 rhomboidal, situated between two basals, the right posterior radial 

 and the second anal. The latter is larger, similar in form to the 

 radials, almost as large, and in line with them. Ventral sac of 

 medium width, composed of very regular hexagonal plates, alter- 

 nately arranged in rows. It is in form of a tube, and ascends 

 almost vertically to about one-fourth the length of the arm, where 

 it bends abruptly towards the posterior side and coils upon itself 

 like a snail. Anal aperture apparently located anteriorly at the 

 very base of the tube. 



Vault composed of a large number of small plates the exact ar- 

 rangement of which has not been ascertained. 



Column round, composed of thin joints. 



Botryocrinus agrees closest with Barycrinus, to the description 

 of which we refer for comparison. 



