CEINOIDS. 169 



Dorycrinus chouteauensis ( Miller). 



Aetinocrinus '^ chouteauemia Miller, 1892: Geol. Hur. Indiana, 18th A.nn. 

 Rep., adv. sheets, p. 18, pi. ili, figs. 9-11. 



Like D. kelloggi but larg'er. 



Horizon and localities — Lower Carboniferous, Kinder- 

 hook limestone : Sedalia. 



Dorycrinus unicornis (Owen & Shumard). 



Plate xxiii, fig. 2. 



Aetinocrinus unicornis Owen & Shumard, 1850 : Jour. Acad. Nat. Sci., Phil., 

 (2), vol. ir, p. 67, pi. vii, fig. 12. 



Aetinocrinus unicornis O'w^n. & Shumard, 1852 : Geol. Sur. Towa, Wis- 

 consin and Minnesota, p. 573, pi vA, figs. 12a-b. 



Aetinocrinus unicornis Hall, 1858 : Geol. Iowa, vol. I, p. 568, pi. x, figs. 

 5a-c. 



Aetinocrinus tricornis Hall, 1858: Geol. Iowa, vol. I, p. 569. 



Aetinocrinus pendens Hall, 1860: Geol. Iowa, vol. I, Supp., p. 31. 



Dorycrinus unicornis Meek & Worthen, 1873: Geol. Sur. Illinois, vol. V, 

 p. 383, pi. vi, figs. 2a-c. 



Calyx subglobular, flattened below, with a long, stout, 

 ventral spine; otherwise like Aetinocrinus in the arrangement 

 of the plates, except that there are three, instead of two 

 ossicles, in the second anal row ; and the ventral opening is a 

 simple aperture in the disk. Arms rather stout, slightly flat- 

 tened at the ends, and with broad spines directed laterally. 

 Surface of calyx plates very convex, rounded — the nodosities 

 developing often into almost pendant tubercles. Besides the 

 large spine on the posterior oral, there are occasionally two 

 smaller ones on other ventral plates directly over the postero- 

 lateral arm -clusters. 



Horizon and localities — Lower Carboniferous, Lower 

 Burlington limestone : Sedalia, Hannibal. 



The typical species of Dorycrinus is provided with six 

 large spines in the disk. Upon this peculiarity, principally, the 

 genus was founded. In this particular the genus must be 

 emended, as there are several other species manifestly belong- 

 ing to the same group which have only a central spine, others 

 three, and still others huge nodosities in place of spines. There 

 G— 12 



