58 



[Senate 



Geological positoin and locality. In the shales of the Hudson-river group : Near 

 Albany. 



GRAPTOLITUS DIVARICATUS (n. s.). 



Stipe bifurcate from the radicle : branches slender, -widely diverging, divergence 

 from 90 to 120 degrees, very slightly increasing in width from the base, serrated 

 on the lower side; serratures nearly straight on the outer margin, with the 

 apices of the denticles somewhat rounded ; the indentation rounded at the bot- 

 tom, extending across one-half the width of the stipe; margins of the indenta- 

 tions thickened : the margin opposite the serratnres is not thickened. 



SuEFACE marked by a row of small nodes placed obliquely to the direction of the 

 axis, and situated just below and a little on one side of the bottom of the serra- 

 ture. Serratures 22 -26 in the space of an inch. 



This species somewhat resembles in its general form, when the stipes are widely 

 divergent, the G. serratulus; but the serratures are on the lower instead of the 

 upper margin of the stipe, and are quite different in form and proportions. The 

 small nodes or tubercles are, also, so far as known, a distinguishing feature. In 

 this species these nodes are distinctly oval in form, and have a depression or slit 

 in the summit; and from their appearance and relation to the serratures, I infer 

 that they are of more importance in the organization than simply as ornament. 



GrAPTOLITHUS DIVARICATUS. 



Fig. 1. A large individual, where the divergence of the parts is much greater than in figure 3. 



The figures are twice the natural size of the specimens. 

 Fig. 2. A part of the stipe still further enlarged, showing the serratures and the small nodes. 

 Fig. 3. An individual, where the divergence is less than 90 degrees. 

 Fig. 4. A part of fig. 3 much enlarged, to show the form of the serrature. 



Geological position and locality. 

 manskill, near Albany. 



In the shales of the Hudson-river group : Nor- 



GRAPTOLITHUS MARCIDUS (n. s.). 



Frond simple biserrate : stipe short, rigid; midrib strong; serrations deep, the 

 denticles small, triangular, subobtuse, arranged in the proportion of twenty-eight 

 to thirty-two in the space of an inch, often somewhat alternating on opposite 

 sides of the stipe, which is terminated below by two or three longer denticles 

 which are of the same substance as the body of the stipe. The apex is marked 

 by an extended fibre or continuation of the axis. 



