134 ECHINODERMATA—PELMATOZOA. SUB-KINGDOM III 
The Radianal (=first or lower anal plate auct.), when present, rests within the re-entrant 
angle of two adjoining basals to the right of the true anal plate, and is the lower half of a 
bisected radial, which only in certain genera assumes anal functions. 
Orals=The five large interradial plates which surround the mouth or cover it. They are 
said to be symmetrical when of nearly the same size aud form ; asymmetrical when the posterior 
plate is pushed in between the four others. 
Aimbulacrals=The rows of small plates in the tegmen which are radially situated. They 
consist of adambulacrals or side-pieces, and the covering-plates (Saumplattchen). The former, 
when present, constitute the outer, the latter the inner rows of plates. The covering plates 
form a roof over the food-grooves ; they are generally represented by two alternating rows of 
small plates, more or less regular in their arrangement, which are movable upon the arms and 
pinnules, but upon the disk only in those Crinoids in which the mouth is exposed. 
The orientation is based upon the natural position of the Crinoid, with the arms uppermost, 
and viewing the specimen from the anal side. The anal interradius will then be posterior, the 
radius opposite to it anterior, while the right and left sides correspond with right and left of 
the observer. 
Primary Divisions of the Crinoidea, according to W. and Sp. 
iE 
Crinoids in which the arms are free above the radials. The topmost joint the 
youngest in the stem.—Order 1. INapuNATA. 
(a) Disk composed of orals only. Ambulacra subtegminal.—Sub-Order A. Larviforiia. 
(4) Posterior side of the disk extended into a sac. Ambulacra suprategminal.—Sub-Order 
B. Fistulata. 
1B 
Crinoids in which the lower brachials take part in the dorsal cup. All plates of 
the calyx united by close sutures. Mouth and food-grooves closed. The top joint 
the youngest in the stem.—Order 2. CAMBERATA. 
Lat, 
Crinoids in which the lower brachials are incorporated into the calyx either by 
Jateral union with each other, or by means of a skin studded with calcareous particles. 
All plates from the radials up movable. Mouth and food-grooves exposed. The top 
stem joint fused with the infrabasals, and not the youngest joint of the stem—Order 3. 
ARTICULATA. 
(a) Arms non-pinnulate-—Sub-Order A. Jmpinnata, 
(4) Arms pinnulate.—Sub-Order B. Pinnata.] 
Order 1. LARVIFORMIA. Wachsmuth and Springer. 
(Haplocrinacea, Newumayr.) 
Tegmen formed by five triangular orals only, arranged in the form of a pyramid, 
Dorsal cup composed of basals and radials exclusively, except in the Cupressocrinidae, 
where the basals enclose a central undivided plate. All plates immovably united by 
close sutures , arms feebly developed. Ordovician to Carboniferous. 
Mostly small forms exhibiting embryonic characters persistently throughout 
life. 
Family 1. Haplocrinidae. Roemer. 
Calyx small, pyriform to globose. Three of the radials compound, the others simple. 
Orals large, triangular to pentagonal, laterally in contact. Arms five, wniserial, non- 
pinnulate. Devonian. 
