HEXACRINIDiE. 795 



the upper end than at the lower, and stouter in the middle than along the 

 margins. The sockets in which they rest have not been observed, but must 

 have been large, and probably extended to near the arm bases. Anus sub- 

 central. Column round and small. 



Horison and Locality. — Kaskaskia group ; Crittenden Co., Ky. 



Type in the Lyon collection. 



Remarks. — Lyon described this species as having but one " primary 

 radial/' and two series of " secondary radials," of which the first series is 

 said to consist of two, the other of four plates. He overlooked the small 

 costal, and regarded the two succeeding rows, which are partly distichals 

 and partly palmars, as " secondary radials." He further supposed the wing- 

 like appendages to be composed of three pieces ; but the fact is that the 

 suture lines indicated in his Figure Yb on Plate 3 are cracks in the specimen, 

 and that plate evidently does not belong to this species. 



Pterotocrinus coronarius Lyon. 

 Plate LXXIX. Figs. 7a, b. 



1857. Asterocrims (?) coronariMS — liYO^ ; Geol. Kep. Kentucky, Vol. III., p. 476, Plate 1, Figs. 1, Iff. 

 1839. Pterotocrinus coronarius — Lton and Cass., Syn. List Palffioz. EcUaod. (Proceed. Amer. Acad. 



Arts and Sci., Vol. IV., p. 302). 

 1881. Pterotocrimis eoronatus — W. and Sp. ; Eevisiou Palaiocr., Part II., p. 91 (Proceed. Acad. Nat. Sci. 



Pbila., p. 265). 



The structure of the dorsal cup is not known,* but the parts pi-eserved 

 are so characteristic of the genus, and again differ so essentially from the 

 same parts of all other known species, that there can be no doubt that they 

 belong to a distinct species. The tegmen is remarkable for the extravagance 

 of its winged processes, which project out almost horizontally from the calyx, 

 and form with it, as seen from above, a five-rayed petaloid star. The petals, 

 viewed from above, are broad, narrowest at the extremities and slightly 

 bending downward ; the margins of the iipper face curve \ipward and form 

 a well defined rim around the median portions. The appendages are massive 



* This species was described by Lyon from a single " unique crinoidal fragment," having, as he said, 

 "neither basal, radial, nor arm plates." This is the type specimen wliich tvc have figured, and no other 

 is known to have been discovered. Yet it is a singular fact that there is in the Museum of Comparative 

 Zoology at Cambridge a lead cast of what seems to have been the same specimen, but having the missing 

 dorsal portion of the calyx intact and showing all the characters of the genns. This cast is supposed to have 

 been given to Professor L. Agassiz about 1850 ; but whether it was made from a partial restoration of the 

 specimen which afterwards became Lyon's type, or from anotlier almost duplicate specimen, or whether the 

 type was complete as originally found, and the dorsal cup broken off and lost before Lyon's description was 

 made, can only be conjectured. 



