Paleontology of the Cincinnati Group. 



99 



ARTICLE XII.— MANUAL OF THE PALEONTOLOGY 

 OF THE CINCINNATI GROUP. 



By Joseph F. James, M. D., M. Sc., P. G. S. A. 



PART VIII. 



(Continued from Vol. XVIII, p. 140.) 

 Division B. Pelmatozoa.* 

 Class 3. crinoidka. 



This is by far the largest class of Echinodermata in our 

 region and includes many beautiful forms. In some localities 

 they are remarkably abundant, and whole layers of rock are 

 frequently made up of their stems. The animals have lived 

 from the earliest Silurian times to the present, and the anat- 

 omy of the extinct forms may be fairly inferred from the living 

 ones. The features of the class are as follows : 



Body fixed during a portion or the whole of the life of the 

 animal to the sea bottom by means of a flexible jointed col- 

 umn or peduncle, springing from the center of the dorsal or 

 aboral surface, cup-shaped or discoidal, with the dorsal surface 

 protected by a system of calcareous plates ; mouth in the 

 upper surface, generally in the center; jointed, flexible ap- 

 pendages or arms, springing from the margin of the cup- 

 shaped body, primitively five in number, and having lateral 

 processes or pinnuks; the upper (or ventral ) surfaces of the 

 arms furnished with grooves in which are situated the repro- 

 ductive organs ; sometimes, however, these are in the pin- 

 nules, or, in living forms, beneath the skin.f 



In the arrangement of the genera and species of our section 

 the classification adopted by Wachsmuth and. Springer (Re- 

 vision of Palseocrinoidea) has been followed. Considerable 



* This includes forms possessing stalks. 



f Nicholson, Manual of Paleontology, 1889, Vol. I, pp. 408, 409. 



Jour. Cin. Soc. Nat. Hist., Vol. XIX, No. 3.) I 



Printed Nov. 13, 1897. 



