Bemarks on the Trenton Limestone of Kentucky. 157 



lington, Iowa, well known as a student and collector of the Crinoids, 

 and aatlior of the Revision of the Palceocrinoidea^ one of the most im- 

 portant works 3' et issued, treating of this difficult group of the Echino- 

 derma. 



SCAPHIOCRINUS SPINIFER, UOV. sp. 

 (Plate v., fig. 3> symmetrical side.) 



Under Basals — Not shown in any of the specimens thus far col- 

 lected. 



Basals — Five, hexagonal, three being slightly higher than wide, 

 pointed above, and semicircularly truncated below. The one on the 

 right of the azj^gous side is truncated above for the support of the con- 

 tiguous radial, and laterally where it meets the lower plate of the azy- 

 gous series. The one on the left of this area is similar to the three 

 first described, but slightly narrower and longer. 



Badials — Five, pentagonal, nearl}^ equal in form and size, the one 

 on the right of the azj^gous area slightly smaller than the other four. 

 These plates are all truncated above and pointed below, the pointed 

 lower extremity being coincident with the basal siltures, except in the 

 case of the one noted above, of which the lower extremity rests upon 

 the basal as in tj^pical Poteriocrinus, The upper articular face of 

 these plates extends entirely across, and is their widest part. This 

 face has, near its outer margin, a longitudinal furrow, which extends 

 about two thirds its length, 



A similar groove occupies a like place in the lower articular surface 

 of the brachials, and these doubtless are the points of attachment for 

 some portion of the apparatus by means of which the arms were moved 

 outward, this freedom of motion being indicated by the gaping suture 

 joining the radials and brachials. 



Brachials — Five, pentagonal, about as wide as high, equal in size, 

 laterally constricted, the upper outer side, below the articulating sur- 

 faces prolonged into a blunted or round-pointed spine, a character re- 

 peated in each of the bifurcating plates succeeding the brachials. 

 These form rows of spines around the specimens as may be seen from 

 the figure. The lower articulating face extends entirely across the 

 brachials, and is furrowed as stated above in describing the radials. 



Azygous Plates — Of these but the lower two are shown, and they 

 have the arrangement of the corresponding plates in typical Poterio- 

 crinus. 



Arms — Of these there are ten at the top of the brachials. They 

 divide again on the seventh and eighth plates above these (this num- 



