156 NEW YORK STATE MUSEUM 



terradial plates. Lower brachials forming a part of the calyx; cost.^ 

 hexagonal, cost.^ pentagonal, axillary bearing the distichals. In- 

 terradials lying chiefly between the costals. Arms 10 to 20, biseriaL 

 Stem round. 



Thysanocrinus liliiformis Hall (Fig. 50) (1852. Pal. N. Y. 2:188^ 



pl- 42) 



Distinguishing characters. Surface of plates ornamented by verti- 

 cal or radiating, interrupted or crenulated, sharp, elevated striae; 

 small infrabasals, large basals and still larger radials; three distichals 

 in each of the 10 arms, the lowest large and hexagonal, the others 

 cuneiform, followed by the biserial upper arm plates; stem joints 



round and alternatingly thin and 

 ,^^' ^ ^\ tiiick, most irregular near the 



i base of the calyx. 



Found so far only in the 

 Rochester shale at Lockport 

 (Hall), but may also occur at 

 Niagara. 



Genus lyriocrinus Hall 

 [Ety : A6/)jov, small lyre; x/)cVr>v, lily], 

 (1852. Pal.N. Y. 2:197) 

 Calyx depressed, with a dicy- 

 clic base. Infrabasals five; ba- 

 sals five, pentagonal^ truncated 

 at the upper end. Radials sepa- 

 rated all around by large inter- 

 radials, which scarcely differ 

 from the anal interradius. Anal 

 aperture eccentric. Plates of the 

 calyx smooth or finely granu- 

 lose. Tegmen almost flat, com- 



Fig. 51 Lyriocrinus dactylus ^^^^^ ^^ ^ ^^^^^ HUmbcr of Small 



plates. Arms 10, strong, simple and biserial. Stem round. 



Lyriocrinus dactylus Hall (Fig. 51) (1852. Pal N. Y. 2:197, 

 pl. 44) 



Distinguishing characters. Stem near the calyx of alternating- 

 larger and smaller joints, the larger projecting much beyond the 



