564 NORTH AMERICAN INDEX FOSSILS. 



192. I. laevis Conrad. (Fig. 1900.) Siluric. 

 Plates with lower margins obtusely triangular and upper margin 



with a corresponding reentrant angle. 

 Rochester (Niagaran) of New York. 



LXXIII. Lecanocrinus Hall. 

 Similar to Ichthyocrinus, but only four of the rays laterally in 

 contact, the 'two posterior R being separated by a rhomboidal 

 radianal and a somewhat larger IRA. Siluric. 



193. L. macropetalus Hall. (Fig. 1901, 1902.) Siluric. 

 Calyx subglobose. Stem slender, smooth; thick joints alternat- 

 ing with thin ones at irregular intervals. 



Rochester shale of New York. 



Fig. 1902. Lecanocrinus macroj>etalus, Q.na\ys\s oi caXyx. (After Hall. ) 



LXXIV. Taxocrinus Phillips. 



Similar to Ichthyocrinus, but all 5 R separated by interbrachials. 

 Posterior B larger than the others and truncated, supporting an 

 IRA which is followed by a longitudinal row of small supple- 

 mentary anals interposed between numerous minute irregular 

 pieces. Ordovicic-Mississippic. 

 194. T. elegans (Billings). Ordovicic. 



Calyx small and conical, with arms one and one half inches high. 



Trenton of Ottawa. 



