CLASS III 



CRINOIDEA 



193 



Encahjpfocrinns, and sharing the same distribution in the Silurian ; not known 

 in the Devonian. 



- 1 B C 



Fk;. 293. 



CcMici-inus coslatus (Hising.). Siluiian ; Gotluiul. A, Crown. B, Calyx showing the construction of the 

 tegrnen. C, Inner or ventral aspect of the base. £», Outer or dorsal aspect of the .same. Natural size (after 

 Angelin). 



Chicagocrinws Weller. Like CalUcrinus, but the primibrachs (costals) 

 reduced to a single diminutive plate in each ray. Silurian ; North America 

 (Chicago area). 



Family 7. Batocrinidae Wachsmiith and Si^ringer. 



Monocyclic. The lower brachials forming an important jiart of the dorsal cup. 

 Radials in contact except at the posterior side, where they are separated by a hepta- 

 gonal anal plate, followed by three plates in 

 the second range. Base hexagonal. Rays ry 



usually branching by equal bifurcations. c'ycy 



Tegmen composed of numerous small, un- Ol^^'^ ^^ 

 differentiated plates. Ordovician to Lower 

 Carboniferous. 



Subfamily A. Periechocrininae. 



o^o 



O«^0a^ 



RlCb 



Tanaocrinus W. and Sp. Interbrachials OvV'rs^ A>\ v^/ ^^l}/7n 



lerous, indefinitely arranged in de- cTyo r^ '^ V^ y Or^ 

 ;sed areas passing gradually into the cT^ ^ cC^^ 0^ Q^ 



numer 



pressed areas passing gradually into the 

 tegmen, leaving brachials in ridges con 

 tinning to the free arms ; posterior area 

 divided by median ridge of anal plates 

 resembling brachials. Arms uniserial 

 with ossicles more or less cuneate, tend- 

 ing to interlock distally ; branching be- 

 yond the calyx. Calyx elongate. Basals 

 five. Column round, or sub-pentagonal. 





Fig. 294. 



Batocrinus sp. Lower Carboniferous. Analysis 

 of calyx ; b, Basals ; E, Radials ; ihr, Interbr.achials ; 

 SX, supplementary anal ; X, Special anal plate 

 (after W. and Sp.). 



Ordovician (Cincinnatian) ; Ohio. 



Xenocrinus^ S. A. Miller. Basals four. 



Arms not branching. 



Column 



^ Better specimeus obtained since the preijaration of Wachsmuth and Springer's Monograph 

 show clearly not only that the interbrachials in this genus are definite plates with close sutures, but 

 VOL. I O 



