DESCRIPTIONS OF NEW SPECIES OF FOSSILS FROM 

 THE TRENTON GROUP OF NEW" YORK, 



BY C. D. WALCOTT. 



Genus GLYPTOCRINUS, Rail. 



Glyptocrenus argutus, n. sp. 



Plate 17, fig. 9. 



Calyx small and somewhat pentangular from the depression of the 

 interradial areas. Underbasals apparently obsolete. Basals five, 

 pentagonal, more than twice as wide as high. Plates of first ring 

 of primary radials wider than high, heptagonal, the upper margin 

 slightly concave to receive the convex basal margin of the second 

 series, the plates of which are hexagonal, their upper margin bearing 

 the pentagonal plates of the third series of primary radials upon which 

 the first bifurcation takes place. Fifteen plates above another bifurca- 

 tion occurs, every alternate plate between bearing a rather long jointed 

 pinnule that in very young specimens has the form of a small 

 armlet. 



Interradial area occupied by three series of plates of one, two and 

 three plates respectively, above which none were observed. A single 

 plate occurs between the first two plates above the first bifurcating 

 plate. 



Surface of plates a little roughened but not granulose. 



Column of medium size, round, and formed of alternating thin and 

 thick plates, the latter having a projecting denticulated margin. 



The calyx of the specimen from which the above description is 

 drawn has a width of 3.5 m m . at the summit, and a height of 2.25 m m . 

 up to the first bifurcating plate. A specimen about three times as 

 large has the basal plates a little higher in proportion to the width 

 and the radial plates are marked by an elevated rounded ridge which 

 bifurcates on the third radial. The upper series of interradials is also 

 ornamented by three narrow crenulated ridges crossing each other at 

 the center of each plate. A specimen intermediate in size to this, also 

 the one figured, presents these characters in a slight degree. 



Formation and locality. Upper portion of the Trenton limestone 



Trenton Falls, New York. 



