On a Fossil Fern from the Lower Coal-measures of Nova Scotia. 485 



vation of the land previous to the period of the great-mammalian 

 fauna, when its present contour was mainly given, was not gradual ; 

 and that, after subsequent depressions, there have been sudden eleva- 

 tions since that period. 



Lastly, it was pointed out that sudden vertical movements of the 

 surface on a grand scale are of as probable occurrence as those 

 lesser movements with which we are historically acquainted, be- 

 cause, both in the case of strata previously unbroken and in that of 

 strata once faulted but at rest, the pressure requisite to rupture or 

 to fold them will accumulate enormously before they yield to it, 

 when, after some slight slow and gradual movements, they will be 

 thrown up or down with a sudden movement, with or without 

 flexures, as the case may be. Thus, by mechanical considerations, 

 the author is led to believe that the ordinary nature of movements 

 of the earth's crust must be sudden. 



2. " On an undescribed Fossil Fern from the Lower Coal-measures 

 of Nova Scotia." By Dr. J. W. Dawson, F.G.S. 



In a paper on the Lower Carboniferous rocks of British America, 

 published in the 15th volume of the Geological Society's Journal, 

 Dr. Dawson noticed some fragmentary plant -remains which he re- 

 ferred with some doubt, the one to Schizopteris (Brongn.), and the 

 other to Sphcereda (L. and EL). With these were also fragments 

 of a fern resembling Sphenopteris (Cyclopteris) adiantoides of Lindley 

 and Hutton. Since 1858 the author has received a large series of 

 better-preserved specimens from Mr. C. F. Hartt ; and from these he 

 finds that what he doubtfully termed the frond of Schizopteris is a 

 flattened stipe, and that the leaflets which he referred to Sphenopteris 

 adiantoides really belonged to the same plant. Mr. Hartt's speci- 

 mens also show that what Dr. Dawson thought to be Sph&reda were 

 attached to the subdivisions of these stipes, and are the remains of 

 fertile pinnae, borne on the lower part of the stipe, as in some modern 

 ferns. This structure is something like what obtains in the Cuban 

 Aneimia adiantifolia, as pointed out to the author by Prof. Eaton, 

 of Yale College. No sporangia are seen in the fossil specimens. 



Dr. Dawson offers some remarks on the difficulties of arranging 

 this fern among the fossil Cyclopterides, Noeggerathice, and Adian- 

 tites ; and, placing it in the genus Cyclopteris, he suggests that it be 

 recognized as a subgenus (Aneimites) with the specific name Acadica. 



The regularly striated and gracefully branching stipes, terminated 

 by groups of pinnules on slender petioles, must have given to this 

 fern a very elegant appearance. It attained a great size. One 

 stipe is 22 inches in diameter, where it expands to unite with the 

 stem ; and it attains a length of 21 inches before it branches. The 

 frond must have been at least 3 feet broad. The specimens are ex- 

 tremely numerous at Horton. 



The author then notices that the long slender leaves so common in 

 the Coal-measures of Nova Scotia, and hitherto called Poacites, though 

 sometimes like the stipes of Aneimites, are probably leaves of Cordaites. 



On some specimens of Aneimites Acadica, markings like those made 

 by insects have been observed ; also a specimen of the Spirorbis 

 carbonarius. 



