UTICA SLATE. 517 



latter fossil is rare in the limestone, but is exceedingly abundant in the slate. The whole are 

 confined chiefly to the lower part of the rock, the upper part being non-fossiliferous. 



The fossils which are found in this rock, and which have not been seen in the Trenton 

 limestone, or in any lower position, are the following : 



No. 1. Beck's triarthus (Triarthus beckii), the head of which, from its frequent occurrence 

 in the slate without its body, is the reason why it alone is figured ; but the entire animal will 

 appear in the Report on the fossils of the State. It is the characteristic fossil of this slate, 

 existing in great numbers in some locahties ; but it is not exclusively confined to this rock, 

 a few heads having been seen towards the upper part of the Frankfort slate. 



No. 2. Dentated graptolite (Graptolites dentatus), is in great abundance : very few locali- 

 ties are destitute of it. To this fossil, in all probability, the slate owes its dark color, which 

 is due to the carbonaceous matter composing the fossil. This species extends into the rock 

 above, unless there be a difference, which is yet to be determined. 



No. 3. Utica trocholite, should it b^different from the Trocholithus ammonius of the Tren- 

 ton hmestone. It is in greater number on East Canada creek, just above Manheim bridge. 

 It is usually compressed, and about the size of the ammonius. The one figured is smaller, 

 rather less than half the usual size, being about one inch in diameter, and apparently a young 

 individual. It was found on Canajoharie creek. 



A long slender orthoceras is frequently found in the slate ; it resembles the Striated ortho- 

 ceras of the Trenton rock . 



The Ladder graptolite, (Graptolites scalaris), has been seen in this slate, but it is a rare 

 species ; a few specimens only have been found, none of which could be obtained in time to 

 be executed in wood. It is well named, consisting of two elongated parts, connected by cross 

 bars placed at regular distances. 



The Triarthus beckii, as before asserted, is a very constant associate of this slate, but it is 

 rare to meet with more than the head or fragments of the body and tail of this animal. The 

 best locality, and where numbers of perfect ones have been found, is at the old mill-dam, 

 below the junction of Oxtungo creek, about four miles south of Fort-Plain. The first ever 

 discovered that were perfect, was in the creek to the east of Utica. A few have been found 



Geol. 3d Dist. 8 



