BATOCRINID^. 491 



posed of two series of ninety or more joints to each series. Interbrachials : 

 1, 2, 3; the first very short and small for the genus, not rising to the full 

 height of the first costals ; the two of the second row twice as long as the 

 first and very narrow ; the plates of the third range quite variable in form 

 and size, and partly interambiilacral. First anal plate larger than the radials, 

 and longer than wide ; deeply truncated at the upper angles for the support 

 of two large, elongate interbrachials, which enclose a narrow second anal. 

 There are four to five plates in the next range, which are followed by nume- 

 rous small, irregular pieces, forming a fiattened area containing the anus, 

 which is directed obliquely upwards ; the plates of this area grow smaller as 

 they approach the anus, which is located midway between the posterior oral 

 and arm regions, and opens out laterally. Ventral disk depressed conical ; 

 the orals and radial dome plates large and covered with heavy rounded 

 nodes, which extend over the whole surface of the plates ; the intervening 

 pieces are comparatively small and but slightly convex. Posterior oral 

 extremely large, and separated by small perisomic plates from the other 

 four, and similar plates are interposed between the latter, so each oral is 

 isolated. There is one large radial dome plate over each anterior ray, and 

 two over each posterior one, the second plate being placed above the division 

 with two arms. The interambulacral plates are quite numerous, and cover 

 over the oric^in of the ambulacra. 



Horizon and Locality. — Upper part of the Keokuk group ; Keokuk, 

 Iowa, and Hamilton, Ills. 



Type in the (Worthen) Illinois State collection, Springfield. 



Remarks. — This species is readily distinguished from A. americanus by 

 its larger size, the hexangular form of the first costals, the different arrange- 

 ment of the interbrachial pieces, the isolated condition of the orals, and the 

 flatness of the anal area. 



Agaricocrinus excavatus Hall. 

 Flate XXXIX. Figs. 3, 4, 5. 



1S61. Agaricocrinus excavatus — Hall; Prelim. Desor. New Spec. Crin., p. 3. 

 1861. Agaricocrinus ^Amphoracrimis) excavatus — Hall; Bost. Journ. Nat. Hist. Vol. YII., p. 282. 

 1877. Amphoracrinzts excavatus — S. A. Miller ; Catal. Amer. Palseoz. Foss., p. 70. 

 1893. Agaricocrinus excavatus — Whitfield; Mem. Amer. Mus. Nat. Hist., 1893, Vol. I., p. 26, Plate 2, 

 Pigs. 14, 15. 



Smaller than the two preceding species. Calyx pyramidal, a little wider 

 than high ; the radial portions projecting outward and downward so as to 



