ART. 22 PAGECRINUS, A NEW CRINOID GENUS KIRK 3 



The infrabasals are pentagonal in outline and are relatively large. 

 The basals are very large in proportion to the size of the cup and 

 the other constituent plates. All are hexagonal in outline except 

 the posterior, which is heptagonal. In the case of the posterior basal 

 the normal acute angle above is truncated to act as a base of support 

 for plate X . The radials are pentagonal in outline and are relatively 

 very small in size. The radial facet extends the full width of the 

 radial and shows at the surface as a straight horizontal line. Anal X 

 is of about the same height as the radials and somewhat narrower. 

 It is quadrangular in outline. In one specimen there appears to be 

 a low plate equal in width to X and lying between X and the pos- 

 terior basal. This plate may not have an existence in fact but be 

 due to a very regular horizontal fracture of X . There are no signs 

 of it in any other specimen where the posterior interradius is shown. 



The arms bifurcate regularly on the fourth primibrach, giving 

 rise to two equal rami, which in turn bear ramuli. In the right 

 anterior ray of one specimen the arm branches on the third primi- 

 brach, and in another specimen the third primibrach is axillary in 

 the right posterior ray. This seems to be a sporadic variation, not 

 having been seen in any other specimens examined. The ramuli are 

 long and stout and are borne on alternate sides on each second 

 secundibrach. The ventral groove of the arm is covered by two rows 

 of small slightly overlapping and interlocking ambulacrals. They 

 average about three in number to each side of an arm ossicle. 



The ventral sac is of about the length of the arms and in its distal 

 portion is stout and circular in section. In its proximal portion on 

 the dorsal side is a median row of heavy plates, scarcely to be dis- 

 tinguished from arm ossicles, except that they are somewhat nar- 

 rower and shorter. Above, the tube is made up of five or six vertical 

 rows of fairly large plates. In one specimen the ventral sac appar- 

 ently curves outward between the arms and extends some 7 milli- 

 meters beyond the crown. Whether this is normal can not be told. 

 This specimen was lifted from the rock in an effort to determine its 

 structure, but without success. In another specimen which has its 

 posterior interradius exposed the ventral sac can be traced for a 

 distance of 9 millimeters. It then apparently plunges downward 

 into the rock as if assuming a horizontal attitude. It seems probable 

 that the ventral sac does normally have this flexed form and assumes 

 a horizontal attitude at about one-half its height. 



Horizon and locality. — All of the known specimens come from the 

 Jeffersonville limestone (of Middle Devonian — Onondaga age) near 

 St. Paul, Ind. 



Types. — The types are in the Springer collection in the United States 

 National Museum. 



