PALAEONTOLOGY OF IOWA. 483 



to the fifteenth or seventeenth plate. The arms (outer side 

 of the figure), have their first bifurcation on the eighth 

 plate from the base. 



A small axillary plate is intercalated between the arms at 

 the first, and sometimes in the second bifurcation. 



This neat and symmetrical species differs sufficiently from the known Cyathocrinus 

 in the character of its base, and resembles none of the previously described Ameri- 

 can crinoids, so far as I know. 



Fig. 3. View of a specimen imbedded in argillaceous limestone. 



Geological formation and locality. In shaly limestone of the age of the 

 Hamilton group : New-Buffalo, Iowa. 



GEKUS 



For generic description, see SYNBATHOCR.INUS under the head of 

 Crinoidese of the Burlington limestone. 



Synbatliocrinus matutinus (n.s.). 



PLATE I. FIG. 2, 



BASAL plates undivided, forming a slightly projecting disc 

 in the specimen : first radial plates wider than long ; second 

 radials longer than wide, obtusely angular along the centre ; 

 brachial plates quadrangular, and subangular longitudinally 

 along the centre : column round, composed near the base of 

 alternating larger and smaller rings. 



The only specimen seen is a fragment, imperfect at the upper extremity, with 

 the surface much broken-, and particularly the basal and first radial plates, 

 while the surface of the arm-plates has been exfoliated. The structure, therefore, is 

 not very satisfactorily determined, though the peculiar form of the crinoid and the 

 succession and arrangement of the plates are sufficient to distinguish it from any 

 other established genus of crinoids. 



Fig. 2. View of an imperfect specimen imbedded in shaly limestone. 



Geological formation and locality. In shaly limestone of the age of the 

 Hamilton group, associated with Strophodonta demissa : New-Buffalo, Iowa. 



