494 PALEONTOLOGY OF NEW-YORK. 



and Shaepe in tlie Quarterly Journal of the Geological Society of London, Vol. ii, 



pa. 276, pi. 41; but the general features here shown are apparently common to 



many Spiriferse of the Higher Silurian or Lower Devonian beds. 



Fig. 1 a, h. Dorsal and front views of a specimen in which the shell is partially csfoliated. 

 (The mesial fold ia more angular in the specimca than ia represented In the 

 figure.) 



Fig. 1 c. The ventral valve of another specimen, in which the plications are rounded. 



Fig. 1 e. A ventral valve which is more extended on the hinge-line, and preserves to a con- 

 siderable degree the surface markings, and has about eight plications on each side. 



Fig. 1 y. A ventral valve of proportionally greater length : the plications are broad and 

 roujided, and seven are visible on each side. 



Fig. 1 g. Profile view of a gibbous specimen. 



*Fig. 1 h. An enlargement of the surface, showing the fine concentric and radiating striae as 

 they appear on a worn surface. 



Fig. 2 c. The dorsal side of a cast, in which the plications are sharply angular. 



Fig. 2 h, c, d, e. Casts of the ventral valve, showing a variety of form and markings in the 



oast of the muscular impression, and in the number and development of the 



plications. 



Fig. 2/1 Cardinal view of a cast which Is somewhat distorted, and shows a part of the 



ventral valve : the beak is broken off. 



Fig. 2 ^. A cardinal view of the cast of a ventral valve, showing the elevation of the procesa 

 filling the beak. 



Fig. 2 A. A similar view, showing also the ventral side and the median line. 



Fig. 2 t. The cast of a distorted specimen. 



Geological position and localities. In the Oriskany sandstone, everywhere in the 

 State of New-York, and at Cumberland ( Marylaiid ). 



8{)ii'ifei' intcnuedius ( n. s.). 

 Shell transverse, semielliptical ; the ventral valve moderately and re- 

 gularly convex, area of medium height, foramen large ; mesial sinus 

 of moderate depth, rounded. Dorsal valve unknown. 

 SuEFACE (of a specimen one and a half inches wide) marked by ten 

 depressed plications on each side of the mesial sinus. 

 The dental lamellae are not at all or but slightly thickened : the mu- 

 scular impression is broad and strongly striated, with sometimes a filling 

 of the cavity of the beak. 



This species has been recognized in a few imperfect specimens of the ventral 

 valve; but its regular convexity, more numerous rounded and little elevated pli- 

 cations, with a somewhat shallow sinus, distinguish it at once from the S. arrectus 

 with which it is associated. 



Geological position and locality. In the Oriskany sandstone : Cumberland, Md. 



