HEXACRINID.E. 



DICHOCRINUS MuNSTEE. 



1S3S. MuNSTEK ; Beitr. zur Petrefactenkunde, I., p. 2. 



1843. Austin ; Monogr. Eec. and Foss. Crinoids, p. 45. 



1850. D'Orbigny; Prodr. de Paleont., I., p. 156. 



1852. Owen and Shumaed; Geol. Rep, Iowa, Wise, and Minnesota, p. 589. 



1S53. De Konixck and Le Hon; Eecli. Crin. Cavb. Belg., p. Ii6. 



1857. PiCTET; Traitede Paleont., Vol. IV., p. 333. 



1860. Meek and Worthen ; Proceed. Acad. Nat. Sci. Phila., p. 381. 



1860. Hall; Suppl. Geol. Eep. Iowa, p. 83. 



1860. Cassedat and Lton (in part) ; Proceed. Acad. Arts and Sci., Vol. V., p. 16. 



1861. Hall ; Post. Jonrn. Nat. Hist., Vol. XII., p. 288. 



1862. Dujahdis and Hdpe ; Hist, naturelle des Zoophytes IicMn., p. 155. 

 1862. White ; Proceed. Post. Journ. Nat. Hist., Vol. IX., p. 19. 



1866. Meek and Wokthen ; Geol. Eep. Illinois, Vol. II., pp. 167 and 263. 



1879. Zittel; Haudb. der Palaeontologie, Vol. I., p. 365. 



1881. W. and Sp. ; Eevision Palieocr., Part II., p. 81. 



1882. De Loriol; Paleont. Franjaise, Criaoides, Part I., p. 33. 



1883. Woetfen ; Geol. Eep. Illinois, Vol. VII., p. 313. 



1885. W. and Sp. ; Eevision Palaiocr., Part III., p. 119 (Proceed. Acad. Nat. Sci. Pbila., p. 341). 



1890. W. and Sp. ; Geol. Eep. Illinois, Vol. VIII., p. 190. 



1890. S. A. MiLLEK ; North Araer. Geology and •PalfEontology, p. 239. 



Not Hall 1858; Geol. Rep. Iowa, Vol. I., Part II., pp. 654 and 689; nor Shumard 1857; Trans. 

 St. Louis Acad. Nat. Hist., Vol. I., p. 5. 



Syn. FMycrinm (in part) — Phillips ; Geol. of Yorkshire, Vol. II., Plate 3, Figs. 24 and 26. 



Syn. CotyUdonocriims — Cass, and Lton. 1860, Proc. Am. Ac. Arts and Sci., V., p. 26. 



Calyx oblong, conical to almost cylindrical. The dorsal cup consists 

 almost exclusively of basals, radials, and a large anal plate. The costals and 

 distichal.?, although laterally connected by interbrachials, and taking part in 

 the composition of the calyx, more or less, retain the form of arm plates. 

 Plates delicate ; their surfaces smooth, or covered with longitudinal strife or 

 rows of small tubercles. Basals two, the suture line running from the anal 

 plate to the anterior radial. They form together a deep obconical or rounded 

 cup, which in height often equals the length of the radials. Eadials large, 

 subquadrangular, except the anterior one, which is pentangular ; their upper 

 faces excavated for the reception of the brachials. Costals two, very short 

 and narrow. In some species the axillary costals support the arms, in others 

 those of the distichals or palmars, and the first and second jjlate of each 

 order are united by syzygy. Arms thin, either uniserial or biserial, some- 

 times pendent. Pinnules unusually long and rather stout. Interbrachials 

 three, arranged transversely ; they rest upon the upper faces of the radials 

 and are succeeded by a number of interambulacral pieces. The covering 

 plates of the ambulacra generally exposed and forming continuous rows. 

 Anal plate frequently a little smaller than the radials, pentangular, narrower 

 at the upper end than at the lower. Anus excentric, placed within a wart- 



95 



