A NEW DEVONIAN CRINOID GENUS — KIRK 6 



in outline, supporting two tube plates on its upper sloping shoulders. 

 The other basals are pentagonal in outline with a maximum width 

 slightly in excess of the height. The radials have a width approxi- 

 mately equal to the height. The horseshoe-shaped arm-facet has a 

 width about three-fifths that of the upper surface of the radial. The 

 right and left posterior radials abut laterally against the first pair of 

 tube plates, and each supports a tube plate of the second range on its 

 inner upper shoulder. The plates of the dorsal cup appear to have 

 been devoid of ornamentation. 



Nothing is known of the arms beyond the first bifurcation. In the 

 left posterior ray the primaxil is the tenth brachial, in the left anterior 

 ray the ninth, and in the right posterior ray probably the tenth. The 

 arms were apparently isotomous in their division. In the left posterior 

 ray the primibrachs range in length from 1.3 mm to nearly 2.2 mm 

 and have an average width of about 1.7 mm. The arms are nonpin- 

 nulate, and the food-grooye is covered by a double row of covering 

 plates. The brachials are perforated by an axial canal. 



The anal tube is subcylindrical in section with a diameter of about 

 3 mm a few millimeters above the top of the dorsal cup. In its upper 

 portion as preserved it is apparently composed of five vertical series of 

 tube plates which in part are laterally apposed and in part imbricate. 

 At the base of the anal tube two of the tube plates rest on the upper, 

 sloping, subequal shoulders of the posterior basal without the inter- 

 position of a special anal plate. In the second range there are three 

 tube plates. Of these the outer pair rest in part on the upper inner 

 sloping shoulders of the right and left posterior radials. 



The column is subcircular in section, with a very wide lumen. At a 

 distance of 5 mm from the cup the column has a diameter of approxi- 

 mately 5 mm. At this point the columnar wall has an average thick- 

 ness of but 0.5 mm in its thinner portions. A camera lucida outline 

 drawing of the column in cross section is given on the plate. From this 

 it can be seen that the lumen has a tetramerous structure. The exact 

 outline of the inner wall is obscure, owing in part to crushing and 

 perhaps in part to solution. There are four approximately equidistant 

 ridges projecting from the wall into the lumen. These were grooved 

 medially. To either side of the groove appear to have been lateral 

 extensions, giving the ridge the appearance of a bifid column in section. 

 It is possible that these flanges connected laterally, forming discrete 

 camerae. If so, the encircling walls were probably very thin. The 

 columnals are low, one of the thickest seen measuring but 0.7 mm 

 in height. 



The specific name is given in honor of Dr. Carl Rominger, one of the 

 pioneers in mid-western American Devonian paleontology, to whose 

 collecting ability we owe the present specimen. 



