^ 



f^ 



CLINTON GROUP. 



GRAPTOLITES. 



39 



I have detected two species of Graptolites in this group : One of them was kno^^^l and 

 published in the Report of the Fourth Geological District, 1843 ; the other is new. Thus far 

 all our examinations have not sufficed to bring out a single species of Graptolithus from any 

 more recent period than the Clinton group. This genus must therefore be ranked among those 

 families which, though living in great profusion in early geological periods, never prolong their 

 existence into the modern periods even of the paleozoic era. In all our more recent formations 

 of Silurian and Devonian age, we have nothing which represents the Graptolite : we bid a fare- 

 well to the genus. 



416. 15. GRAPTOLITHUS CLINTONENSIS. 



Pl. a. XVII. Fig. i a-i. 

 Graptolithus clintonensis. Geol. Rep. 4th Dist. N. York, 1843, p. 74; fig. 12, p. 72. 



Stipe slender, simple, linear, straight or cur^•ing, serrated on one side, the opposite side (or 

 back) marked by a fine longitudinal groove ; serrse long, deeply cut into the stipe, with the 

 points recurved ; surface slightly granulated? 



This species is readily distinguished from any in the lower strata, by its long recurved teeth, 

 wliich are very peculiar. When the points of these are imperfect, its distinctive characters rest 

 on the depth to which they are cut into the stipe, and their close arrangement, which likewise 

 distinguishes this one from those in the lower rocks. In specimens where the back of the stipe 

 is shown, it presents a longitudinal groove ; and at the base of the teeth it becomes much ^^ • 



thicker, and again diminishes towards the points. .^|P^ 



Fig. 1 a. A lamina of slate, with fragments of this species upon the surface. Where imbedded 



in the soft green shale, the depth of the serratures and the pointed extremities are 



not so clearly preserved. 

 Fig. 1 i. A fragment of a stipe, showing the depth of the serratures and the curved extremities. 

 Fig. 1 c. A similar fragment, showing the opposite side. j|L, 



Fig. 1 d. A small fragment which is less flattened, the axis more solid, and the teeth appearing 



shorter. 

 Fig. 1 e & 1 /. Enlargements from the previous figure. 

 Fig. \ g. A small fragment of the same species, showing some small nodes at the base of tho 



teeth. 

 Fig. 1 ^. A portion of 1 g enlarged. 

 Fig. 1 i. The back of the stipe enlarged, showing a slight groove. 



Position and locality. This species is very abundant in the upper green shale of the group 

 at Sodus, Wayne county; also in the eastern part of Williamson, and in the banks of the 

 Genesee river at Rochester. (State Collection.) 



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