538 THE CRINOIDEA CAMEEATA OF NORJ'H AJilEEICA. 



as also the ainbulacral plates, except near the outer margins of the tegmen, 

 where well defined covering and side pieces are on a level with the interam- 

 bulacrals ; and similar pieces occur along the arms. The covering plates are 

 quite regular in their arrangement, forming a sort of ridge with a row of 

 side pieces at each side. Anus excentric, at the top of a short, rounded or 

 conical protuberance. Column large, giving off lieavy branches at the distal 

 end ; it increases but little in width, and is composed throughout of alter- 

 nate thick and thin joints. Central canal moderately large, obscurely penta- 

 lobate, and proportionally wider at the lower end. 



Horizon and Locality . — Kinderhook group ; Le Grand, Marshall Co., 

 Iowa. 



Type at Pasadena, California, but authentic specimens are in the 

 collection of Wachsmuth and Springer. 



Remarks. — Megistocrimis jmtvus has the same affinities with M. nohilis as 

 " Actinocrinus" brevicornis with Mecjistocrinus Evansi, and we regard it a 

 young stage of that species. The arms are free above the distichals, and 

 it has less interbrachial plates. The specimen, Plate LI., Fig. 8, is some- 

 what abnormal, having but one costal in two of its rays. 



Megistocrinus latus (Hall). 

 Plate XLVIII. Figs. 3a, b. 



185S. Hall; Geil. Rep. Iowa, Vol. I., Part II., p. 4S0, Plate 1, Figs, la, b. 

 1381. W. and Sp. ; Revisiou Palseocr., Part II., p. 138. 



A large species. Dorsal cup short, about twice as wide as high, abruptly 

 depressed at the bottom ; the sides expanding upwards ; arm bases slightly 

 projecting; plates flat and without ornamentation; suture lines grooved. 



Basals closely anchj'losed, rather large, located at the bottom of an 

 inverted cup, which is a little wider than the column. Radials about as 

 wide as long; their lower ends abruptly curved to form the sides of the 

 basal concavity, the other portions spreading horizontally and constituting 

 the bottom of the calyx. First costals generally longer than the second. 

 Distichals in the antero-lateral rays three, supporting two ai'ms ; the other 

 rays have a single axillary, followed by several palmars with four arms to the 

 ray. Interbrachials : 1, 2, 3, 3, and some small pieces between the arm 

 bases. The first anal jjlate, which is a little narrower than the radials, is suc- 

 ceeded by three plates, and these by numerous irregularly arranged pieces, 



