524 NORTH AMERICAN INDEX FOSSILS. 



XXXIII. AcTiNOCRiNus J. S. Miller. 

 Calyx pear-shaped or ovate. Plates of dorsal cup ornamented 

 with radiating ridges passing from plate to plate and often meeting 

 a node. B three, equal, forming an hexagonal cup. Three of the 

 R six-sided, the posterior pair seven-sided. First costals nearly 

 as high as v^ide; second costals axillary, supporting both distichals 

 and palmars, and frequently higher orders of brachials. IR very 

 numerous, passing insensibly into the tegmen. Tegmen formed of 

 thick, tubercled, hexagonal plates produced into a tube with anus 

 at the end. Arms biserial and given off in clusters from five 

 protuberant lobes. Pinnules long, slender, and laterally in con- 

 tact. Column round, long. Mississippic. 



79. A. verrucosus Hall. (Fig. 1849.) Mississippic. 

 Plates of dorsal cup tumid and nearly all elevated into a promi- 

 nent node whence often radiate obscure ridges. 



Upper Burlington of Illinois, Iowa and Missouri. 



80. A. tenuisculptus McChesney. Mississippic. 

 Small (dorsal cup less than one half inch high). Resembles 



A. verrucosus in proportions of calyx. Plates of cup delicate, 



Fig. 1849. Actinocrinus verrucosus. Fig. 1850. Aciinocyinus lowei, X %- 

 (After Hall, Geol. Iowa, I., 2.) (After Hall, Iowa Geol., I., 2.) 



slightly tumid, beautifully ornamented with radiating ridges form- 

 ing a star on each side and two on the anal side. 



Lower Burlington of Missouri, Iowa and New Mexico. 



81. A. scitulus Meek and Worthen. Mississippic. 



Below medium size. Somewhat resembling A. verrucosus but 

 with less convex ventral disk, forming only one third of the height 

 of the calyx; the arm extensions are shorter, and the interbra- 

 chials less numerous. 



Upper Burlington of Missouri, Illinois and Iowa. 



