52 SMITHSONIAN INSTITUTION 



While S. pratteni, in its extraordinary size and the anomalous develop- 

 ment of the interbrachial areas, represents the culmination but evidently not 

 the close, of the genus, it is interesting to note that there is a progression in 

 these characters within the species itself. The strata containing it consist of 

 blue and grey limestones in the lower part, passing into cherty beds above. 

 It is in the latter that the largest specimens with the greatest and most abrupt 

 interbrachial projections are found; while those from the lower bluish lime- 

 stones are in the average smaller and of a distinctly less rugose type. 



The species was described from a fragment in which but a small part of 

 the calyx was preserved, and the leading characters were not disclosed. In 

 his original description McChesney stated that the horizon and locality of the 

 unique type specimen were not clearly known, but it was supposed to have 

 been from the Carboniferous limestone somewhere in Alabama. The horizon 

 is, of course, wrong; but as the same Linden beds in which the Hardin County 

 specimens occur extend along the Tennessee River into northwestern Alabama, 

 there is no doubt that the type specimen was derived from the same source. 



Holotype. — Originally in the Chicago Academy of Science, was destroyed 

 by fire, but is represented by casts in the American Museum of Natural History, 

 New York; the Walker Museum of the University of Chicago; and in the 

 author's collection at the National Museum. The other specimens here figured 

 are in the author's collection. 



Horizon and locality. — Helderbergian ; lower or middle part of Ross 

 limestone of the Linden formation; Hardin County, Tennessee, at various 

 localities along Horse Creek, near Grandview on the Tennessee River, and 

 probably also in northwestern Alabama. The species occurs in the upper 

 25 or 30 feet of a series of blue-grey and cherty limestones with clay partings, 

 of a total thickness of about 60 feet, in which are also found Camarocriniis 

 of maximum size. It is not found at Pyburn's Bluff, where similar beds of 

 cherty limestone exist, but evidently lack the pratteni member, which may at 

 that locality lie below the water's edge. 



6. SCYPHOCRINUS PYBURNENSIS n. sp. 

 Plates VII, figs. 2a, b, 3 ; VIII, figs. 6a, b, 7 



Calyx large, elongate; low-convex in lower part, widest below secundi- 

 brachs, contracting and cylindrical toward the arm-bases; height to width at 

 zone of greatest width and to that above, 2.75 to 2.20 to 2. Interbrachial areas 

 slightly protuberant, giving an obtusely pentagonal cross-section at that level, 

 and unsymmetric by reason of greater and rather irregular enlargement of 

 posterior interradius, which usually has two or three additional plates above 



