REPORT ON THE CRINOIDEA. 145 
X.—ON THE RELATIONS OF THE NEOCRINOIDS TO THE 
PALASOCRINOIDS. 
The term “ Neocrinoidea,” which was first introduced by the writer in 1881,! embraces 
all the “ Crinoidea Articulata” of Miller and Miller, together with Marsupites and Holopus, 
both of which were placed elsewhere by the German zoologist; while the Paleozoic 
Crinoids generally were referred to by him as the “Crinoidea Tessellata,”? this group 
including the Semiarticulata and Inarticulata of Miller. His definitions of these two 
great groups, however, were meagre in the extreme. The Articulata comprised the genera 
Pentacrinus, Aprocrinus, Encrinus, and Comatula in the wide sense, i.e., types in which 
the radii are free down to the base of the calyx; while his only distinct reference to the 
Tessellata is that they are Crinoids “deren Kelch ganz aus Tafeln zusammengesetzt ist.” * 
From his numerous references to individual genera, however, it is possible to obtain a 
tolerably clear notion of the ideas which led Miiller to establish these two principal 
divisions of Crinoids; and various palzeontologists have in consequence attempted, with 
more or less success, to formulate characters which should distinguish them from one 
another. 
The most satisfactory of the earlier attempts in this direction was that which appeared 
in Bronn’s Thierreich (vol. ii. p. 228). Besides the supposed sutural union of the calyx- 
plates and the presence of a subtegminal mouth in the Tessellata, reference is also made 
to the asymmetry of the calyx in this group, the more frequent presence of a dicyclic 
base, and the greater rarity of stemless forms than in the Articulata. 
On the other hand, Liitken* and others have pointed out the weakness of these 
definitions. 
By far the best of the numerous diagnoses which have been drawn up since the time 
of Miiller are those which we owe to Zittel.? But the freedom of the rays in the Articulata, 
on which Miiller laid stress, is omitted by him, while an important error runs through his 
as through all the earlier definitions. The calyx plates of the Tessellata are “ unbewéglich 
durch einfache Nahte verbunden;” while those of the Articulata are “ meist sehr dick, 
durch gelenkartig ausgehéhlte und gewoélbte oder ebene Nahtflichen verbunden.” Now 
the lowest articulation to be found in the calyx of an articulate Crinoid is that which 
unites the first and second radials (Pl. LXII.). The former are suturally united both to 
one another and to the basals; while, when underbasals are present (Marsupites, 
Extracrinus), the union between them and the basals is of the same kind. In both 
groups the interradials (when present) are suturally united to the radials and to one 
another ; so that the name-giving difference between the Articulata and the Tessellata is 
1 Ann. and. Mag. Nat. Hist., 1881, ser. 5, vol. vii. p. 296. 2 Pentacrinus, loc. cit., p. 30. 3 Thid., p. 29. 
4 Op. cit., pp. 219-222. 5 Paleontologie, pp. 335, 342, 345. 
(ZOOL. CHALL. EXP.—PART xxxul.—1884.) 19 
