CLASS I CRINOIDEA 125 
the dicyclic forms are properly termed Jasals, and the lower series widerbasals 
(infrabasals). The basals as thus defined are equivalent to the “ parabasals” in 

Euspirocrinus spir- 
alis, Ang. Stalked 
Crinoid with dicyclic 
base and anal inter- Fic. 220. Fic. 221. 
radius. «a, Anals; b, 
Basals; ib, Infrabasals. Actinocrinus proboscidialis, Hall.  Pro- Poteriocrinus multiplex, 
(Right and left sides jection of calyx showing the three basals Traut. Calyx with dicy- 
reversed, after An- (b), 5X3 simple radials (7), four paired inter- clic base, radials, costals, 
gelin.) rays (ir), and a fifth unpaired anal interray (). and distichals. 
the older nomenclature of Johannes Miiller, and to the “subradials” of de 
Koninck and other authors. 
Both basals and infrabasals are primarily five in number ; but owing to the 
fusion of two or more of the proximal plates, the number of basals in the 
monocyclic forms may be reduced to four, three, or even to two, and that of 
infrabasals in the dicyclic to three. During the 
ontogenetic development of the recent Antedon, a ee aS OF 
oi! , ; ©) 
more or less complete resorption of the basals has r/ |» rt) 
been observed ; and the same probably also held ye eae 
true for certain Mesozoic genera (Hugeniacrinus, ( me ib \ ee | >] 
: b ~ \ 
Phyllocrinus). In many of the non-pedunculate aby ies 
Crinoids (Uintacrinus, Marsupites, Fig. 222) an il EDS 
rentron ib VOR 
A \ \ 
additional plate known as the centrodorsal rests 7 FEA CSANES 
against the infrabasals, and probably represents ey, LCE 
an atrophied stalk. The basals are united with Gaul 
one another and with the overlying radials by se 
close sutures, and are immovably held together 
by fibrous connective tissue. Though usually — arsupites testudinaris, Schlot. sp: 
smooth, the joint faces are sometimes striated, jFH ues) Basiss s Raliale 
and are visible externally as incised lines. 
b. Succeeding the base is a cycle of five (rarely four or six) plates, which, 
on account of their position with reference to the rays, are called radials. The 
radials form the sides of the calyx in nearly all Mesozoic and Recent Crinoids, 
and give origin directly to the arms, which may become free immediately above 
the radials, or may be incorporated for some distance in the calyx, either by 
means of supplementary plates, or by lateral suture among themselves. 
