m. 



4() 'paleontology of NEW-YORK. 



417. 16. GRAPTOLITHITS VEN0SUS(7i.^jB.). 



Pl. a. XVII. Fig. 2 a,b, c. , 



Stipe rather broad, linear, rigid, serrated on both sides ; serrse short, acute, distant, the spaces 

 between curving into the substance of the stem ; substance composed of reticulated or venose 

 threads. 



This very peculiar species differs from all the others in a sufficient degree to be readily 

 identified. The substance is very thin and fragile, and scarcely recognizable without a glass ; 

 but when once the peculiar venose structure is discovered, it is readily detected afterwards. 

 The peculiar serrffi, or emarginations of the two margins, is also a very peculiar and distinctive 

 feature. By these characters the smallest fragment is readily distinguished, and its difference 

 from all known species is at once clearly observable. 



Fig. 2 a. A piece of slate, with numerous fragments of G. dinionensis and G. verwsus. The latter 

 are much more indistinct than the former, and can scarcely be brought out without a 

 magnifier. 



Fig. 2 6. A fragment of G. venoms enlarged. 



Fig. 2 c. A fragment (enlarged), which appears to be the upper extremity of the stipe of this 

 species. With the exception of this figure, no terminations of either species have been 

 seen. They occur in fragments of various lengths, having a pretty uniform character 

 throughout. 



Position and locality. This species occurs with the preceding one in the same thin black 

 layers in the green shale below Rochester. (State Collection.) 



101. 2. CH.ETETES LYCOPERDON. 



PL. XVn. Figs. 1 a-l. 



A species, which I am unable to distinguish from the one in the Trenton limestone and 

 Hudson-river group, occiu's in considerable numbers in the Clinton group. In this position, 

 however, it never attains those massive hemispherical forms which are so abundant in the Trenton 

 limestone. It is almost always found in the branching form ; and the others, though sometimes 

 seen, are thin, and never attain any considerable bulk. 



Fig. 1 a. The upper surface of a flat massive form. 



Fig. 1 b. Figure showing the height of the same specimen. 



Fig. 1 c. The lower surface of the same specimen. 



Fig. 1 d. Section of a small hemispheric mass. 



Fig. 1 e. Several columns enlarged. 



Fig. If. Openings of cells enlarged. 



Fig. 1 g-. A ramose specimen on limestone. 



Pigs. 1 h, i, k. Sections of the branches of several ramose specimens through the centre, and on 



one side of the centre, showing the arrangement of the cells. 

 Fig. 1 /. Several of the cells enlarged. 



i 



