268 THE CRINOIDEA CAMEHATA OF NORTH AMERICA. 



1881. W. and Sp. ; Revision Palseocr., Part IL, p. 185 (Proceed. Acad. Nat. Sci. Phila., p. 359). 



1883. W. and Sp. ; Amer. Journ. Sci., Vol. XXV., pp. 255 to 268. 



1883. S. A. Miller; Amer. Journ. Sci., Vol. XXVL, pp. 105 to 113 ; and Cincin. Soc. Nat. Hist., Vol., 



VI., pp. 220 to 228. 

 1885. W. and Sp. ; Revision Palaeocr., Part III., p. 102 (Proceed. Acad. Nat. Sci. Phila., p. 324). 

 1859. S. A. MiLLEii ; North Amer. Geol. and Palaiont., p. 247. 



Not GlT/ptocrinus D'Oebigny, 1852; Cours element, de Paleont., Vol. II. , p. 142, nor Prodrome, 



Vol. I., p. 47. 

 Not Qlyptocri7ius Hall, 1863, Trans. Albany Inst., Vol. IV., p. 202; nor 28th Rep. N. Y. State 



Mus., p. V62 = Mariacrinus. 

 Not Ghjptocrinus Hall, 1872; 24th Rep. N. Y. State Cab. Nat. Hist., p. 20& = Reteocrims. 

 Not Glyptocrbms Hall, 1872; ibid., p. '^^1 ■=zPtychocrinus. 



Not Glypfocrimis Wetherby ; Journ. Cincin. Soc. Nat. Hist., Vol. IV., p. 83 = Reteocrinus. 

 Not Glyptocrinus S. A. Miller; ibid.. Vol IV., p. 74 = Compsocrinus, nor p. 75 = Reteocrinus. 

 Not Glypfocrlms Etheridge and Nicholson, 1880, Silur. Poss. of Girvan Distr., p. 328. 

 Syn. Fossil Encrinife A.-^'YiB.o-^Y, 1838; Amer. Journ. Sci., Vol. XXXV., p. 405. 

 Syn. Icosidadylocrinites Owen, 1843 (Catalogue name). 

 Syn. Pycnocrinus S. A. Miller ; Journ. Cincin. Soc. Nat. Hist., Vol. VI., p. 231. 



Calyx obconical or subglobose; plates thin, often highly ornamented; the 

 fixed brachials passing imperceptibly into arm plates, and the interbrachials 

 into disk plates ; the arms rising vertically from the edge of the tegmen. 



Basals five, of uniform size, forming a small cup. Eadials and costals of 

 nearly equal size ; the second costal hexagonal. Distichals varying in num- 

 ber, there being but two in species in Avhich palmars take part in the calyx ; 

 but when the second bifurcation takes place in the free arms, they are quite 

 numerous, frequently six to eight or more in the calyx, followed by several 

 others in the free arms. When this is the case, the second distichal gives 

 off a large pinnule ; while in the other the proximal pinnule is developed 

 into an arm. Arms rarely branching beyond the second bifurcation, rising 

 vertically from the calyx ; they are long, slender, rounded on the back, 

 and composed of a single series of short, slightly wedge-shaped pieces, 

 which do not interlock. Pinnules slender, closely arranged ; the proximal 

 ones the stoutest, and frequently incorporated into the calyx. 



Interbrachials definitely arranged ; the first large, resting upon the slop- 

 ing upper faces of the radials ; there being two plates in the second row, and 

 two, sometimes three, in the higher ones. The anal side widest, having 

 generally three plates in the second and all succeeding rows. Interdistichal 

 spaces large, composed of numerous small plates ; some species also have 

 interpalmars. Ventral disk depressed-hemispherical, very slightly extend- 

 ing above the level of the arm bases ; the ambulacra subtegminal, except 

 near the periphery, where some of the small covering pieces are exposed, 

 but the course of the ambulacra is indicated by surface ridges. Plates 

 of the disk very minute and irregularly arranged, decreasing in size toward 



