HEXACRINID^. 781 



side inward. Both horns of the crescent give off cirri from alternate plates, 

 communicating with the axial canal of the stem, which is oval, its long dia- 

 meter at right angles to the curvature of the column. There are no cirri in 

 the upper part of the stem ; they commence at some distance from the calyx, 

 and are restricted to the convoluted part. In specimens with a closely coiled 

 stem, the ends of the cirri meet in the centre, and resemble the spokes of a 

 wheel ; they are stout at the proximal end and extremely long, being com- 

 posed of thirty or more pieces, of which the five proximal ones are longer 

 than wide, the upper somewhat shorter. 



Horigon and Locality. — Kaskaskia group, near Sloans Valley, Pulaski 

 Co., Ky. 



Tt/pes in the collection of Wachsmuth and Springer. 



TALAEOCRINUS W. and Sp. 



1881. W. and Sp. ; Eevisiou Palseoci-., Part II., p. 85 (Proceed. Acad. Nat. Sci. Pliila., p. 259). 

 1883. S. A. Miller; Catal. Auiei-. Pateoz. Poss. (Second Edit.), 288. 



1SS5. W. and Sp. ; Xlevision Palicoci-., Part III., p. 120 (Proceed. Acad. Nat. Sci. Phila., p. 313). 

 1889. S. A. Millek; N. Amer. Geol. and Palreout., p. 285. 



Syn. Viclocrimis (in part) — Suuhakd; Trans. St. Louis Acad. Soi., Vol. I., p. 71. 



Syu. Dichocrinus (iu part) — Ciss. and Lton; Proceed. Amer. Acad. Arts and Sci., pp. 16-23. 



Syn. Pterolocnims (in part) — S. A. IMiller ; Catal. Amer. Palseoz. Foss. (Pirst Edit.), p. 89. 



Specimens small. Calyx, as a rule, higher than wide ; the ventral disk 

 as high as the dorsal cup ; the plates thick and devoid of ornamentation. 



Basals two, of equal size and similar form, the suture between them 

 passing from the anal plate to the anterior radial ; they form together 

 a shallow cup, which is more or less transversely elongate, and somewhat 

 excavated at the bottom ; the superior margin of the cup octagonal, six 

 angles being salient and two retreating, the latter directed to the sides 

 which correspond to the longer diameter of the base. 



Radials five, enclosing an anal plate of the same size or even larger; four 

 of them having slightly convex lower faces ; while the anterior one is angular 

 below. The upper faces are somewhat excavated in the middle, and trun- 

 cated at the outer ends. Costals one, very small, often completely hidden 

 from view by the distichals ; when visible, triangular in outline. Distichals 

 one or two, small ; their lower faces resting obliquely against the costals; 

 their sides touching the radials. The third order of brachials supports the 

 free arms, of which there are four to the ray. The arms, so far as observed, 

 are simple and biserial. 



