498 NORTH AMERICAN INDEX FOSSILS. 



g. Rays (radials and lower brachials) laterally in contact on all sides. 



LXXIL Ichthyocrinus. 

 g. Four of the rays in contact, the two posterior being separated by an RA 



and an IRA LXXIII. Lecanocrinus. 



g. Rays all separated by interbrachials 66. 



66. Arms spreading and talon-like, LXXV. Onychocrinus. 



66. Arms rather closely apposed gg. 



gg. Both TRA and RA present LXXVI. Forbesiocrinus. 



gg. Only IRA present LXXIV. Taxocrinus. 



g. Radials separated by interradials but the succeeding rays laterally in 

 contact except at anal side where there is a longitudinal row of anal plates. 



LXXI. Cleiocrinus. 



4. Arms pinnulate LXXVII. Uintacrinus. 



Of doubtful classification. 



Anchor-shaped, with lateral processes LXXX. Ancyrocrinus. 



Broadly shield-shaped, concave I^XXIX. Aspidocrinus. 



Pear-shaped or spheroidal channeled bodies of numerous plates. 



LXX. Carnarocrinus. 



Order I. LARVIFORMIA Wachsmuth and Springer. 

 I. PisocRiNUS Angelin. 

 Calyx small, globose or cup-shaped and composed of heavy 

 plates. B 5, unequal, forming a triangle which is largely sunken 

 in the basal cavity. Following this triangle 

 are three large plates, one on each side and 

 forming most of the calyx ; two of these plates 

 are R and the third, the inferradial, is fol- 

 lowed by two R. The fifth R is a small inter- 

 FiG. 1807. Pisocrinus calated plate. All of the R are deeply ex- 

 milligani. (After Miller ^^^^^^^ centrally for the insertion of the 

 '^^^'^'' arms. Tegmen rarely preserved, but consist- 



ing of five large, symmetrical orals, above which rises a long, nar- 

 row anal tube. Arms long and composed of extremely elongate, 

 heavy, cylindrical joints. Siluric. 



1. P. milligani Miller and Gurley. (Fig. 1807.) Siluric. 

 Of medium size, resembling P. gorbyi, but larger and shorter 



in proportion to its diameter. Calyx obpyramidal, truncated below, 

 and with a deep columnar pit, expanding in the radial regions and 

 pentalobate in summit view. 

 Niagaran of Tennessee. 



2. P. gorbyi Miller. Siluric. 

 Small ; height and width about equal. Summit five-lobed. 

 Niagaran of Indiana. 



