284 S. WELLER FAUNA OF THE FERN GLEN FORMATION 



somewhat strongly convex; above the base of each ray are usually some- 

 what strongly nodose plates, which are more constantly present above 

 the two postero-lateral rays and frequently consist of a series of large 

 plates the upper one of which joins the large, central plate at the summit. 

 The posterior interambulacral area is much larger than the others and is 

 more or less strongly protuberant, the constituent plates being small and 

 irregular; the anal opening is situated near the summit of this inter- 

 ambulacral area and is directed upward. 



The dimensions of two individuals are: Total height of calyx, 16.5 

 millimeters and 14 millimeters; greatest width, 19.5 millimeters and 18 

 millimeters. 



Remarks. — This species exhibits much variation in the convexity of the 

 dorsal cup and in the prominence of the plates of the ventral disk, but 

 may be distinguished from all other members of the genus by its small 

 number of arm bases, there being usually seven, and among the indi- 

 viduals examined never more than eight. The protuberant posterior 

 interambulacral region is also a constant characteristic. 



The species was originally described from the t} r pical Fern Glen beds 

 at Fern Glen, Missouri. 



LOBOCRINUS PISTILLIFORMIS (M. & W.) 



Plate 11, figure 6 



1861. Actinocrinus pyriformis var. rudis M. & W., Proceedings of the Academy 

 of Natural Science of Philadelphia, page 131 (not A. rudis Hall, 

 1860). 



1865. Actinocrinus pistUUformis M. & W., Proceedings of the Academy of Nat- 



ural Science of Philadelphia, page 153. 



1866. Actinocrinus pistUUformis M. & W., Geological Survey of Illinois, volume 



2, page 151, plate 14,. figure 8. 



Description. — Calyx, exclusive of the anal tube, pyriform, being very 

 narrow and apparently cylindrical from the base to the distal extremities 

 of the costal plates, above which the distichals and palmers curve abruptly 

 outward to the base of the arms, forming with the ventricose ventral disk 

 a much expanded visceral cavity entirely above the costal plates. Basal 

 and radial plates not known. First costals very small, a little wider than 

 long, irregularly pentagonal in form so far as seen, one of the sides being 

 much shorter than the others. Second costals axillary, as long as the first 

 and nearly one-third wider ; the only two visible in the type specimen are 

 hexagonal in form, and each supports on its distal sloping sides two dis- 

 tichals of about its own size. Second distichals somewhat larger than the 

 first, each of which supports two palmers, which in turn are succeeded by 



