144 ECHINODERMATA—PELMATOZOA SUB-KINGDOM III 
[The genus Carpocrinus was described by Miller as having no anal plate ; 
but according to Angelin the type-species (C. sempler) has an IRA interposed 
between the radials. It must therefore be referred to Habro- 
crinus, which it resembles in all other respects. | 
Desmidocrinus, Ang. (Fig. 247). Like the preceding, but 
with a greater number of arms, which are longer, and composed 
of shorter joints. Silurian; Gottland. 
Periechocrinus, Austin (Geocrinus, @Orb.) Calyx large, elon- 
gate, somewhat urn-shaped, and composed of thin plates. /? and 
primary r long and narrow, frequently bearing a median longi- 
tudinal ridge. Distichals two; interradials very numerous, the 
second row composed of either two or three plates. Plates of 
the tegmen very small. Anal opening sub-central, sometimes 
prolonged in a tube composed of small, thin plates. Arms 
numerous, slender, branching, biserial; pinnules long and thin. 
Column round, pierced by an extremely large axial canal. 
Fic. 247. Silurian ; Gottland, England, North America. 
Desmidoerinus Megistocrinus, Owen and Shum. Devonian to Middle Sub- 
eran Carboniferous ; North America. Abacocrinus, Ang. Silurian ; 
a” etter Europe. — Gennaeocrinus, W. and Sp. Devonian (Hamilton 
i Group) ; North America. 

Family 4. Barrandeocrinidae. Angelin. 
Base monocyclic. Basals three, enclosing an anal plate which supports three inter- 
radials. Arms biserial, recumbent ; pinnules exposed, and directed upwards.  Silu- 
rian ; Gottland. 
Barrandeocrinus, Ang. followed by two costals ; the upper ones giving off 
two heavy arms, which in perfect specimens are so closely folded as to conceal 
the calyx completely. Pinnules very long; their tips bending inward from 
opposite sides. Column cylindrical, and very heavy; axial canal cireular. 
Silurian ; Gottland. 
[This genus is referred by Wachsmuth and Springer to the Batocrinidae 
and the family discontinued. | 
Family 5. Reteocrinidae. Wachsmuth and Springer. 
Monocyelic or dicyclic. Infrabasals, when present, five ; basals four to fiwe. Radials 
separated by a large IRA which supports a vertical row of higher anals all of nearly 
the sume size; the upper ones passing gradually into the tegmen. The spaces to either 
side of this row, as well as the whole of the four other interrays, both in the dorsal cup 
and tegmen, paved with minute, irregularly formed pieces. Ordovician. 
Reteocrinus, Bill. Calyx obconieal ; EHO" and interaxillary areas 
profoundly depressed. JB five, differing considerably in size. B five, large, pro- 
tuberant, hexagonal. and fixed brachials~forming a broad, highly elevated 
ridge, which passes insensibly into the arms. Jf in contact with the 5, and 
consisting of a large number of minute, irregular pieces. 'Tegmen composed of 
numerous, very small, convex plates, irregularly arranged. Arms with strong 
pinnules, and branching in the free state. Column sub-pentagonal. Ordovician ; 
- North America. 
