Dec, 1920] Cystids and Blastoids 65 



tips of these triangular parts tend to be less convergent. Along the 

 sutures between the radials the theca is sufficiently concave to give a 

 distinctly pentagonal cross-section to the upper half of the theca, while 

 the basal part has a triangular cross-section, as is usual in this genus. 



Locality and Horizon. — From the Bainbridge phase of 

 the Niagaran, six miles west of St. Marys, in St. Genevieve 

 County, Missouri. Collected by Doctor Herrick E. Wilson, and 

 numbered 14791 in the collections of Walker Museum at 

 Chicago University. 



Remarks. — The following new species have been described 

 from the Niagaran locality at St. Marys, all by Prof. R. R. 

 Rowley: Cordylocrinus ? dubius, Cyathocrinus ovalis, Lecano- 

 crinus hemisphericiis, Pisocrinus glahelliis, Pisocrinus granulosus, 

 Scenidium ? nodocostatum, and Stribalocystites missouriensis. In 

 addition to these. Prof. Rowley identified two species as 

 Pisocrinus glohosus Ringueberg and Pisocrinus gorbyi Miller. 

 The fauna is regarded as equivalent to some part of the Browns- 

 port formation of western Tennessee. 



Troostocrinus ? dubius and Melocrinus wittenhergensis were 

 described by Rowley from a Helderbergian locality near Witten- 

 berg, Missouri. The Troostocrinus should be re-examined to 

 verify its generic reference. 



Of the species listed, Scenidium nodocostatum belongs to the 

 same group as the species described originally by Hall and 

 Whitfield, from the Louisville limestone of Kentucky, as 

 Orthis nisis. This is not a Scenidium. 



17. Troostocrinus subcylindricus (Hall and Whitfield). 



(Plate III, Figs. 3 A, B, C.) 



Penlremites subcylindrica Hall and Whitfield, Geol. Surv. Ohio, Pal. 2, 1875, 

 p. 129, PI. 6, Fig. 13'. 



As in all other Eublastoidea, 5 fork-shaped radials are supported by 3 

 basals. The bases of the right posterior and left anterior radials rest on 

 the truncated tops of two of the basals, the top of the third basal, 

 occupying the right anterior interradius, being acutely angular. Theo- 

 retically, each of the two truncated basals was formed by the lateral 

 coalescence of two basals. Only the posterior deltoid can be detected 

 readily, the other four being restricted to the extreme tip of the acute 

 interradial areas. The anal aperture opens through the oral extremity 

 of the posterior deltoid. 



In Troostocrinus subcylindricus, the surface of the radials rises on 

 approaching the radial sinuses, the rise increasing toward the lower end 

 of the sinuses. Immediatelv beneath the lower end of the sinuses the 



