1 58 [ Senate 



hinge equalling the greatest breadth of the shell, and terminating 

 in salient angles : dorsal valve convex ; mesial fold prominent, 

 rounded, marked along the middle by a distinct narrow sulcus; 

 beak incurved : ventral valve convex, most prominent at the 

 umbo, sloping somewhat abruptly with a convex curve to the 

 front and anterior lateral margins ; mesial sinus angular, ex- 

 tending from the beak to the front, where it terminates in a 

 rounded projection ; beak pointed, slightly arched ; area mo- 

 derately high, vertically and transversely striate, arcuate, and 

 sloping from the beak to the extremities of the hinge with a 

 concave curve. Surface marked by nineteen or twenty simple 

 rounded plications on each side of the mesial sinus and fold, 

 and crossed by fine regular concentric lines of growth. 



This species may be distinguished by its general neatness and symmetry 

 of form, and the distinct sulcus along the middle of the smoothly rounded 

 mesial fold of the dorsal valve, as well as by the angular character of the 

 sinus of the ventral valve. Sometimes the sloping sides of the ventral sinus 

 show very faint indications of an obtuse flattened fold on each side of the 

 much more distinct angular depression down the middle, so as to give to 

 the sinus, when viewed in some lights, a subplicate appearance. This latter 

 character is, however, often very obscure, and may be overlooked. 



Geological -position and locality. In the shales of the Hamilton group 

 at Eighteen-mile creek, Erie county, N.Y. 



Spirifer marcyi^ ( n. s.)- 



Pal. N.Y. Vol. iv. 



Shell semicircular, width about twice the length ; hinge equalling 

 the greatest breadth of the shell, and terminating in more or 



* Note. At the same time that I receive this proofsheet from the printer, I also 

 learn of the sudden death of Ex-Governor Marcy, to whom I had dedicated this 

 species as a very slight tribute of my profound respect and esteem, though an 

 entirely inadequate expression of the obligations due from science to this eminent 

 statesman, to whom the State of New-York is indebted for the liberal and impartial 

 organization of her Geological Survey; to which, it may be said without prejudice 

 to others who have since done nobly, is mainly due many of the most valuable results 

 to modern science, and the high character acquired by the State for the scientific 

 achievements her generous patronage has called forth. 



