ECHINODERMA TA—CRINOIDEA . 



523 



76. P. depressus Lyon and Casseday. (Fig. 1848.) Mississippic. 



Appendages enormous, flat and knife-like. Anus at top of a 

 central slender cone. 



Kaskaskia of Kentucky and Illinois. 



yy. P. pyramidalis Lyon and Casseday. Mississippic. 



B larger proportionally than in P. depressus and slightly oblong 

 at right angles to the suture. R more rapidly spreading. Ventral 

 disk pyramidal, with slightly concave sides, covered with longi- 

 tudinal grooves for the reception of the arms. Arms unknown. 



Kaskaskia of Kentucky and Indiana. 



Fig. 1848. Pteroiocrinus depressus^ basal view, showing arms and the interbrachial 

 pieces and side and end view of these appendages. (After Meek and Worthen.) 



XXXII. AcROCRiNUS Yandell. 



Calyx urn-shaped, higher than wide. B 2, equal, forming a 

 nearly flat basin. R separated from B by an indefinite number of 

 iupplementary pieces placed in rows and composing the main part 

 of the dorsal cup. R broadly excavated above for the reception 

 of the two small costals and the two distichals. Ventral disk flat, 

 with anal opening near its margin. Arms erect or pendent, with 

 long and closely packed pinnules. 



Differs from Dichocrinus in the introduction of a belt of supple- 

 mentary pieces between the B and R. Mississippic. 



78. A. shumardi Yandell. Mississippic. 



Height of calyx more than twice the width. Supplementary 

 plates in 14 to 20 rings. (Type of genus.) 



Kaskaskia of Kentucky and Illinois. 



