PLATYCRINID &. 685 
slizhtly depressed, Radials moderately spreading and somewhat irregular 
in form; the two posterior ones fully as wide as long, the others a little 
longer; the median portions of the plates abruptly raised, forming a quad- 
rangular elevation of which the margins are parallel to the edges of the 
plates. Costals subtrigonal, rather short. Ventral disk convex, flattened at 
the summit. ‘The orals very large, the posterior one larger than the four 
others; the latter elongate, at the four regular sides of the calyx resting 
against the first row of interradials, of which the middle one is wedged in 
deeply between the radials. The middle plate of the anal side is much 
wider, and supports a number of small plates which form the anus. Ambu- 
lacral plates few upon the disk. Anal opening excentric, directed upwards. 
Structure of arms unknown. 
Horizon and Locality. — Lower Burlington limestone, Hannibal, Mo. 
Type in the collection of Wachsmuth and Springer. 
Remarks. — This species resembles P. subspinulosus Hall, but differs in the 
form of the calyx and in the surface markings. 
The specific name is in honor of Rev. John Davis, of Louisiana, Mo., to 
whom we are indebted for the type specimen. 
(ee ee 
Platycrinus allophylus 8. A. Miter. 
Plate LX XI. Fig. 17. 
1891. §. A. Mizzer; Bull. 4, Geol. Surv. Missouri, p. 9, Plate 1, Figs. 3 and 4. 
A small species, in its form unlike any other Platyerinus. Dorsal cup 
slender, once and a half as high as wide, cylindrical to the top of the basals, 
then expanding gracefully to the arm facets; the lower face broadly truncated. 
Surface of plates apparently smooth; their margins toward the basi-radial 
and interradial sutures slightly beveled; the interbasal sutures rarely visible. 
Basals as long as the radials, forming a cylindrical cup with a short expanded 
rim around the lower end, the bottom truncated, and slightly impressed for 
the reception of the first stem joint, which occupies less than half the dia- 
meter of the lower face. Radials longer than wide, moderately expanding 
above, rounded along the back, depressed at the sides, their facets projecting. 
The latter occupy fully one half the width of the radials, and more than 
a third their length; they are semicircular, are deeply notched at the upper 
end, and directed outward almost horizontally. Costals short and axillary ; 
a 
