BATOCEINIDJE. 413 



Pinnules proportionally large. Interbrachials two to three; the first quite 

 large, rising to the top of the first distichals. First anal plate narrower 

 than the radials ; followed by two rows of three plates, which are arched by 

 the palmars. Ventral disk depressed convex, the interambulacral spaces 

 slightly depressed ; the orals and I'adial dome plates considerably larger 

 and more convex than the intervening plates. Anal tube composed of 

 almost flat pieces ; central, rising considerably beyond the tips of the arms. 



Horizon and Locality. — Lower portion of the Upper Burlington lime- 

 stone ; Burlington, Iowa. 



Ti/2'^ in the collection of Wachsmuth and Springer. 



DIZYGOCRINUS W. and Sp. (nov. gen.). 

 (Aifuyos two abreast, Kptvov a lily). 



Calyx depressed-subglobose, biturbinate or subconical ; the ventral disk 

 generally as high as the dorsal cup, and sometimes considerably higher. 

 Plates smooth, granular, or obscurely striated. Basals very short, forming 

 a slightly projecting circular rim or shallow basin. Radials proportionally 

 smaller than in Batocriims ; the first costals quadrangular, the second pen- 

 tangular or rarely heptangular. The upper brachials either form a con- 

 tinuous ring around the calyx, or are separated (rarely) between the rays 

 by a narrow interbrachial piece ; the faces supporting the arms are excavated 

 into subcircular or lunate facets, which are directed outward. Arms long 

 and biserial, given off from the calyx either singly or in pairs. When the 

 arms are paired, they start from a diminutive axillary, and the proximal arm 

 plates and this axillary rest upon the same facet ; when simple, a large 

 cuneate plate takes the place of the three small pieces. Kegular interra- 

 dials from two to four, at the anal side five to eight. Anal tube almost 

 central, slender, and rarely rising above the tips of the arms. Respiratory 

 openings small. 



Distribution. — This genus, so far as known, is restricted to the Subcar- 

 boniferous of America ; it is represented in the Upper Burlington limestone 

 by four species, reached its climax in the Keokuk group, and disappeared in 

 the Warsaw limestone. 



Type of the genus. — Dizygocrinus indianensis (Lyon and Casseday). 



Eemarks. — Most of the species for which we propose this genus were 

 described originally by Hall under Adinocrinus, whence they were removed 

 by Meek and Worthen, and placed under Batocrinus. Dizygocrinus euconus 



