74 



than high, gradually expanding, convex longitudinally and pro- 

 jecting at the articulating scales. Articulating facets rather 

 large, directed upward, at an angle of about sixty degrees, 

 form more tlian a semicircle, occupy about half the width of 

 a plate and are notched in the central part for the ambulacral 

 canal. 



This species is founded upon four specimens the lai'ger one 

 of which is illustrated. It resembles P. (timosus more than 

 any other described species, but will be distinguished from it, 

 by the higher cup formed by the basal plates, larger truncation 

 for. the column, and more prominent and larger articulating 

 facets for the second radial. We have examined fifteen spec- 

 imens of P. annosns, and the above diiferences are constant, 

 and the species need not be confounded even on a superficial 

 examination. 



Collected by R. A. Blair, in the Chouteau limestone, in Pettis 

 county, Missouri, near Sedalia, and by him presented to S. A. 

 Miller. 



PLATYCRINUS CLINATUS, n. sp. 



Plate /!', Fig. 26, shorter side of a Inrfje specinirv : Fig. 27, 



longer side of same; Fig. 28, longer side of (uio'hcr 



specimen, showing nn interradi<d on the fz'jgous 



side; Fig. 29, shorter side oj same; Fig 



30, longer side of a smaller 



specimen. 



We h;ive examined Wn sjiecimens belonging to this species, 

 ranging in size between tlie larg(>st and smallest specimens 

 illustrated, and we believe the s])ecinion illustrated by figure 4, 

 plate I, Bulletin No. 4, Geo. Sur. Mo., bcdongs to this species, 

 though it is not at hand for re-examination. All of the speci- 

 mens are larger on one side than on the otluT. and the first 

 radials are longer on one side than on the otlu>r, proving that 

 t'lis is the normal condition of the species. The larger side is 

 the azygous side and opposite to the small liasal. The basal 

 l)lates are generally anchylosed, but in the specimens illus- 

 trated we have been able to see the sutures. 



Species below medium size. Calyx with a large truncated 

 base, above which it is abi-uptly constricted and then gi-ulually 



