AKT. 15 THE FOSSIL CRINOID GENUS VASOCRINUS KIRK 11 



show the two proximal arm ossicles, in one case with the covering 

 plates in place. In addition to the specimens cominfj from the 

 type locality at Louisville, Ky., there is one specimen from Columbus,. 

 Ohio. 



P'ollowing are measurements made of the type specimen : 



Heiuht of dorsal cup, 7 mm. 



Breadth of dorsal cup (post. IR to ant. R), 12.7 mm. 



Diameter of stem, 4 mm. 



Heifiht of IBB, 2.3 mm. 



Heisht of BB (average), 3.8 mm. 



Width of BB (average), 4 mm. 



Height of RR (average), 3.8 mm. 



Breadth of RR (average), 6 mm. 



Breadth of arm facet (average), 3 mm. 



Anotlier specimen of averaj^e size gives the following get of 



measurements : 



Height of dorsal cup, 9 mm. 



Breadth of dorsal cup (post. IR to ant. R), 16 mm. 



Diameter of stem, 5 mm. 



Height of IBB. 2.5 mm. 



Height of BB (average), 5 mm. 



Width of BB (average), 6 mm. 



Height of RR (average), 4 mm. 



Breadth of RR (average), 8 mm. 



Breadth of arm facet, 3 mm. 



The largest specimen seen has a breadth of 18 millimeters and a 

 height of 9.5 millimeters. 



Stripped of its surface ornamentation, the dorsal cup is broadly 

 obconical in form, the sides diverging evenly to about the level of 

 the radials and then flaring outward very ,slightly. With the orna- 

 mentation preserved, especially in the case of older individuals, the 

 cup appears more rounded. In most specimens the cup is lower on 

 the anterior side. This gives the theca a lopsided appearance which 

 is very pronounced in the type specimen and is developed to a vari- 

 able degree in different individuals. 



The stem is round and at least in its proximal portion composed 

 of alternate wide and narrow columnals. The lumen appears to bfr 

 pentagonal in outline, with a slight suggestion of lobation. 



The infrabasals are subequal in size. Their lower margins are 

 somewhat produced, forming a lip. Near each lateral margin of an 

 infrabasal is a sharp carina that runs from the lip across to the 

 center of the adjacent basal. The basals are hexagonal in outline, 

 with the exception of the posterior and right posterior, which are 

 heptagonal in outline. The basals vary in size but apparently without 

 a definite plan. The r. post. B supports RA on its upper left 

 shoulder. The post. B supports RA on its upper right shoulder and 



