250 S. W. Ford and W. B. Dwight — Fossils obtained 



B. Joint Report on the Fossils. 



The fossils which form the subject of this joint examination 

 and report were collected by W. B. Dwight on the days of 

 June 12th, June 23d and October 31st, 1S85, at the following 

 localities of metamorphic limestone: (1) The western roof of 

 tunnel No. 192 of the Boston and Albany R B. at Canaan, N. 

 Y. ; and (2) a ledge situated about 2400 feet southerly from the 

 above tunnel. Subsequently, a few slabs of fossiliferous rock 

 from the tunnel were sent from Canaan through Professor 

 Dana, which have furnished us considerable additional inter- 

 esting material. From similar limestone obtained during the 

 same season by Professor Dana, on the farm of E. S. Hall, about 

 two miles northeast of the tunnel, we have also obtained some 

 evidence of organic structure. Although a thorough paleonto- 

 logical study of the region has not yet been made, and our 

 report must therefore be regarded as only preliminary, enough, 

 has nevertheless been seen to convince us not only of the Lower 

 Silurian age of the strata, but to enable us to fix, with a con- 

 siderable degree of probability, their exact horizon. 



Evidences of the extensive metamorphism of the strata have 

 been constantly met with. The rock, though often abounding 

 in fossils, yet presents them, for the most part, under such con- 

 ditions as to render their determination a matter of extreme 

 difficulty. The organisms are, to a great extent, in an exceed- 

 ingly comminuted state, and frequently present the appearance 

 of having been partially dissolved. Many hand specimens of 

 the limestone, and especially transparent sections of it made 

 with much care, appear to strongly indicate the former semi- 

 fluidal condition of portions of the strata. In other cases, how- 

 ever, where the rock has been less altered, the fossils are quite 

 perfect and sharply defined. The greater portion of the speci- 

 mens which we have studied, have been brought to light by 

 means of polished surfaces and transparent rock slices, although 

 a number of them are large and conspicuous fossils. In view of 

 the important bearing of the facts with which we have had to 

 deal, we have exercised great care in our examinations and 

 have spared no pains in our endeavors to arrive at safe conclu- 

 sions. 



We have found, in the material under consideration, the 

 following organisms. 



Echinodermata. — The majority of the slices and polished 

 surfaces prepared by Professor Dwight from the layers in which 

 the smaller organisms occur, are replete with fragments of small 

 crinoidal columns of forms similar to those so frequently met 

 with in well-known localities of the Trenton limestone. Fig- 

 ures 1 and 2 of Plate VII. of which the first is a transparent 



