FOSSILS OF THE BUKLIXGTOX GEOUP. 397 



dented at the corners of the plates. Anns and column 

 unknown. 



Hight of body to top of central node of the vault, 0.80 

 inch ; breadth, 0.96 inch ; hight to arm openings, 0.58 inch ; 

 do. to anal opening, 0.38 inch. 



This species is apparently most nearly allied to M. brevicornfe. Hall 

 (sp.), but differs in having' a greater number of ranges of brachial 

 pieces included as a part of the walls of the body, and these pieces 

 wider and commencing as double series farther down. Its opening is 

 also placed decidedly lower even than the proposed species Act. minor, 

 of Hall, being distinctly below the horizon of the lower edge of the arm 

 openings, and nearly half-way down the side, measuring from the high- 

 est part of the vault. Its larger vault pieces, excepting the middle 

 ones, are also more prominent and pointed. Its body and vault plates 

 are all much more convex, its arm bases stouter, its vault less depressed, 

 and its opening decidedly lower than in M. superlatus, Hall (sp.) 



Locality and position Upper Burlington beds of the Lower Carbon- 

 iferous, at Burlington, Iowa. No. 161 of Mr. WACHSMUTH'S collection. 



MEGISTOCRIXUS (SACCOCRIXUS) WHITEI, Hall. 



PI. 6, Fig. 1. 



Actin. (Megistocrimte) Whitei, HALL, 1861. Jour. Boat. Soc. Nat. Hist., Vol. 7, p. 271. 

 (Burlington Limestone, Burlington, Iowa. Mr. WACHSMUTH'S collection.) 



GEXUS AGAKICOCRIXUS, Troost. 

 AGABICOCRLSUS NODOSUS, M. and W. 



PI. 10, Fig. 7. 

 Agaricocrinus nodostu, MEEK and WORTHEX. Proceed. A cad. Nat. Sci., Phila., 1869, p. 167. 



BODY without the arms, having a truncato-suborbicular 

 general outline, being convex above and broadly truncated 

 below ; under side moderately concave out to the second 

 radial pieces inclusive. Base small, impressed deeper than 

 the general concavity of the under side, and entirely hidden 

 by the column. First radial pieces extending out horizon- 

 tally from the end of the column, and exposing a flat hex- 



