CORNIFEROUS LIMESTONE. 145 



time and place. Some of these fossils are found in two or more periods or rocks, passing 

 over one or two intermediate ones ; like the Strophomena semiovalis, which in this district is 

 found in the Trenton limestone and the sandstone shale of Pulaski, the Utica and the Frank- 

 fort slate and sandstone intervening. Others are more like the Strophomena depressa, which 

 first appears in the Clinton group with the lower iron bed ; disappearing through the whole 

 period of the salt group, water-lime group, and pentamerus limestone ; reappearing in the 

 Catskill shaly limestone, and continuing upwards, but with intermissions, to the corniferous 

 limestone where it ends ; not a trace of it being seen from that rock, in any of the many 

 which succeed to it. From the twofold character of fossil species, care must be used in 

 determining a rock by them. The species must be of the kind whose range is limited to a 

 single rock, and not of that which extends through two or more rocks ; and attention should 

 also be paid to the number, whether few or many. 



Besides the Strophomena lineata, there are but few fossils foimd in the Seneca limestone 

 at the west end of the district. The Odontocephalus selenurus, which at Auburn appears in 

 the layers containing homstone, is found in the Seneca limestone at Rowland's quarry at 

 Springport ; and thus, as to this fossil, unites the two. 



At the east end of this district, I have not been able satisfactorily to identify this rock. 

 The upper layers of the corniferous limestone at Cherry- Valley, and at the Helderberg near 

 Clark's, those which are above the range of homstone layers, are probably to be referred to 

 the Seneca limestone, having found a single specimen of a strophomena resembling the lineata 

 at each of those places in the upper layers. There is no adveintage in retaining the rock, 

 except as relating to the fossils which at the west are contained in it in great numbers, as a 

 ready and well defined mark of the termination upwards of the Helderberg series, and highly 

 convenient at the west end of the district on that account. 



The Seneca limestone is quarried at Marcellus, a few rods to the southwest of the village. 

 The three upper layers, which lie immediately under the shale, are the ones which are 

 extracted ; they are about seven inches thick. Below them are thicker layers, but they do 

 not answer so well. The whole abound with the Strophomena hneata, and form the straight 

 surfaces of the joints of the rock : it forms a wall like hewn stone. 



The general color of the rock is of some shade of brown-black, usually becoming an ash 

 grey when long exposed. At West hill, its fossils often show a pink tinge, which is also 

 exhibited by some of those of the corniferous limestone. 



In the cabinet of David Thomas of Scipio, there is a bone similar in character to those 

 noticed under the head of Onondaga limestone : It is about 7 J inches in length, and l|- in 

 breadth ; it is curved, and terminates in a point at one end ; one side is round, the other angu- 

 lar. It was found in this rock to the south of Waterloo. It was noticed by Mr. Hall as an 

 Ichthyodorulite. This is the third rock in succession at the west where these pecuhar bones 

 have been discovered ; it being remarkable that nothing of an intermediate character to the 

 animal which bore them, and the crustaceans, have yet been discovered in the State, or else- 

 where that has been made known. 



Geol. 3d Dist. 19 



