366 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



Those in which, the ventral disk is highly differentiated, the ' 

 plates being large and heavy, and in which the arms do 

 not branch beyond a minute axillary at the arm opening . . . BATOCRINITES. 



B. 



Those in which the ventral disk is composed of small, irregu- 

 larly arranged plates, and the arms generally branch after 

 becoming free PERIECHOCErNlTES. 



A. BATOCRINITES. 



BATOCRINUS Cassedat. 



1851. Casseday; Zeitscbr. der Deutscli. Geol. Gesellsch., Vol. TL, p. 237. 



1857. PiCTET ; Traite de Paleont., Vol. IV., p. 32i. 



1862. DnjAKDiN and Hupe ; Hist, nahirelle des Zoophytes Echinod., p. 142. 



1865. Meek and Worthen (Subgenus of Aclinocrinus) ; Proceed. Acad. Nat. Sci. Phila., p. 153. 



1866. Meek and Woethen (Subgenus of Actimcrums) ; Geol. Rep. Illinois, Vol. II., p. 150. 

 1869. Meek and Wortuen ; Proceed. Acad. Nat. Sci. Pbila., p. 350. 



1873. Meek and Worthen ; Geol. Rep. Illinois, Vol. V., p. 364. 



1878. W. and Sp. ; Proceed. Acad. Nat. Sci. Phila., p. 329. 



1879. ZiTTEL ; Handb. der Palseontologie, Vol. I., p. 370. 



1881. W. and Sp. ; Reiisiou Palajocr., Part II., p. 162 (Proceed. Acad. Nat. Sci. Phila., p. 336). 



1835. Steinmann; Elemente der Palseontologie, Part I., p. 157. 



1890. S. A, Miller; North Amer. Geol. and Palfeont., p. 227. 



1892. S. A. Miller; Adv. Sheets of the 18th Geol. Kep. Indiana, p. 23. 



Sjn. Aclinocrinus (in part) Shumard, Hall, White, McChesnet, and Meek and Wokthen prior 

 to 1865, Quenstedt as late as 1885. 



Syu. Uperocriims (in pari) Meek and Worthek, 1865 ; Proceed. Acad. Nat. Sci. Phila., p. 153. 



Calyx biturbin'ate to subglobose ; the rays not lobed. Plates heavy, the 

 surface more or less convex and frequently nodose, but otherwise not orna- 

 mented. Basals three, proportionally large, forming a hexagonal cup 

 thickened at the lower margin, and generally projecting laterally. Eadials 

 very large. Costals two, small, quite frequently anchylosed ; the first qua- 

 drangular, almost linear; the second pentangular. Distichals and palmars 

 as large as, or larger than the costals. Palmars are always represented, 

 except occasionally in the anterior ray. The posterior rays frequently have 

 post-palmars, which do not occur in the other rays. Arm openings equidis- 

 tant, directed horizontally. Eespiratory pores twenty, two above each 

 interradiiis, and two to each interdistichal space ; placed at a somewhat 

 higher level than the arm openings. Arms twenty to twenty-six ; in species 

 with more than twenty arms the extra number is divided between the two 



