ORDER V CRINOIDEA—ARTICULATA 173 
Family 8. Pentacrinidae. d’Orbigny. 
Calyx small, bowl-shaped, and with dicyclic base ; but the infrabasals are either 
rudimentary, or completely resorbed in the adult state. The top stem-joint always the 
youngest joint of the column. Basals five, radials five, costals one to two. Teginen 
flexible, studded with small, irregular, calcareous particles or delicate plates. Arms 
strong, numerously branching, 
and pinnulate. Column long, 
pentangular or sub-pentagonal ; 
its outer angles interradially 
directed ; the curt gwen off 
radially. Upper and lower 
faces of the stem-joints orna- 
mented with a quinquelobate 
figure. ‘Trias to Recent. 
Pentacrinus, Miller (Jso- 
crinus, v. Meyer ; Cladocrinus, 
Ag.; Cainocrinus, Forbes), 
(Fig. 290). JB obsolete ; 
costals rarely more than two, 
none of them _ pinnulate. 
Arms very numerously 
divided. Column more or 
less pentangular ; the angles 
of the axial canal, contrary 
to the general rule in dicyclic 
forms, are radially directed, 
so as to correspond with the 
outer angles of the stem. 
Cirri very numerous; stem 
not thickened at its distal 
end. Trias to Recent ; max1- 
mum in Lias. 
Exquisitely preserved 
specimens are found in the 
Lower Lias of England, and 
the Upper Lias in the vicinity 
of Boll and Metzingen, 
Wiirtemberg. A slab con- 
taining no less than twenty- 
four perfect crowns of P. Pentacrinus (Extracrinus) briareus, Mill. Lower Lias; Lyme 
subangularis, Miller, with Regis, Meland atee Goldfuss). a, Stem-joints of P. subangularis, 
- 55 a) hi pper Lias; 6, Column of P. basaltiformis, Mill. Middle Lias. 
long intertwining stems, 1s 
preserved in the Tiibingen Museum. There also may be seen a column 
which Quenstedt traced for over 70 feet, without reaching either end. 
Metacrinus, Carp. Differs from Pentacrinus in that the F are succeeded 
by four to seven costals, of which the first and second form a syzygy. Where 
seven costals are present, the fourth and fifth are also united by syzygy. 
Angles of axial canal interradially disposed, so as to alternate with the outer 

Fic. 290. 
