BATOCEINIDiE. 481 



Horizon and Locality. — Upper Burlington limestone, near Sedalia, Mo. 



Type in the collection of Mr. F. A. Sampson, Sedalia. 



Bemarks. — The obconical form of the cujj, and the almost flat disk, are 

 the leading characters of this species, in which it approaches A. s^nnosuhcs 

 Hall. However, the calyx of that species is deeply grooved at all sides, and 

 the rays are separated by numerous interbrachial plates which pass up to 

 the plates of the disk. 



Aorocrinus helice (Hall). 

 " ■ Plate XLV. Figs. 2 and 5. 



1864. Actiiiocriims helice — Hall; 17tli Rep. N. Y. State Cab. Nat. Hist., p. 53. 

 1878. Actimcriiuis ^e&e — Hall; Geol. Surv. Ohio, Pateont., Vol. 11., p. 163, Plate 11, Egs. 5 to 8. 

 1881. Agaricor.rmus helice — W. and Sp. ; Revision Palaeocr., Part II., p. 112 (Proceed. Acad. Nat. Sci. 

 PMIa. p. 286). 

 Sjvi. Actiiiocri:tus helice. Tar. eris Hall; Geol. Surv. Oliio, Palgeont., Tol. II., p. 164, Plate 11, 



Figs. 9 to 10. 

 Sjn. A/fciricocrims eris — W. and Sp. ; 1881, Revision Palaeocr., Part II., p. 112. 



Approaching in the form of the calyx, and the stoutness of its arms, 

 some of the aberrant smaller forms of Agaricocrinus. Calyx wider than 

 high, the summit crowned with an elongate node or short spine. Dorsal cup 

 short, rapidly spreading to the arm bases, rounded at the bottom, the lower 

 margins of the radials bending inward and taking part in the truncation at 

 the bottom. Surface of plates nodose, the radial ones transversely angular, 

 the interradial ones with obscure radiating ridges along the margins. 



Basals small, arranged almost horizontally ; only small portions of them 

 being exposed in a side view; the interbasal sutures deeply channeled at 

 the lower end. Radials large, rapidly spreading upwards; the upper face 

 slightly notched at the sides. First and second costals together smaller 

 than the radials ; the first quadrangular, the second pentangular. Distichals 

 short, consisting in the anterior ray of three rows of plates in the calyx, of 

 which those of the first row are somewhat larger than the two of the suc- 

 ceeding ones, the latter being as short as the free brachials above, and like 

 them rounded on the back. In the posterior rays both first distichals are 

 axillary, and support from each side two short fixed palmars. In the two 

 antero-lateral rays normally the distichals next to the posterior rays are 

 axillary and support palmars, the others are followed by other distichals; 

 it occurs, however, also that none of them are axillary or both of them ; the 

 number of arms thus varying from twelve to sixteen. Arms rounded on 



