HISTORICAL. 29 
tegmen consists of five large pieces, as in Haplocrinus, ete., these plates are 
orals, and not supplementary pieces as we had supposed. 
The logical consequences of these conclusions were taken up by us in 
1890,* when we undertook to prove that the so-called vault of Palaeozoic 
Crinoids is not a structure sui generis, but a highly differentiated disk; that 
their large, rather regularly arranged interbrachial and interambulacral 
plates represent morphologically the smaller irregular pieces between the 
rays and ambulaera of later forms, and that the Palxozoic and Neozoic 
Crinoids do not differ so essentially from one another as we had supposed. 
It also appeared that neither the closure of mouth and food grooves, nor 
the presence of anal plates, is a constant character among the older Cri- 
noids, and we were compelled in 1888 to abandon the Paleeocrinoidea and 
Neocrinoidea as systematic groups. 
That the two groups could not be upheld, was proved also by Neumayr.t 
who claimed that none of the characters by which they had been separated 
was persistent ; and he proposed in place of them a primary division based 
upon the condition of the mouth and ambulacra, whether sudlegnunal or 
suprategminal, Viz. : 
I. Hypascocrinoidea. Mouth, ambulacral vessels, and Saumpliittchen (the latter if pres- 
ent) beneath the tegmen, 
1. Spheroidocrinacea. Cup mostly, tegmen always, constructed of a large number of 
plates immovably connected among themselves. Generally several of the arm 
plates incorporated into the calyx by means of interradial pieces. Tegmen roof- 
ing the whole ventral surface. Among its plates are readily distinguished a 
central one, and four and two interradial proximals. Anus either directly piercing 
the tegmen, or placed at the terminal end of a plated tube. (This group agrees 
with our Camerata.) 
2. Huplocrinacea. Cup and tegmen composed of a small number of immovable pieces. 
The former having but one radial, and no interradials except an anal. Tegmen 
with a central plate. (Our Larviformia.) 
38. Ichthyocrinacea. Cup and tegmen composed of very numerous, somewhat movable 
pieces; the former having two basal rings and more than one order of radials. 
(Our Ichthyocrinide.) 
Il. Epascocrinoidea. Ambulacra not covered by the tegmen; their furrows exposed or 
closed by Saumplittchen. 
1. Cyathocrinacea. Base generally dicyelic. Cup without interradials at the four 
regular sides. Teemen, so far as known, composed of five orals, which support at 
their edges the ambulacra; the latter covered by Saumpliittchen, Anus within the 
ventral sac. (Our Fistulata.) 
* Perisomic Plates of the Crinoids (Proceed. Acad. Nat. Sci. Phila., October, 1890, pp. 345-375). 
+ Die Stamme des Thierreiches, Wien und Prag, 1889, pp. 438-460. 
