119 
SPIRIFER undulatus. 
TAB, DLXIL- fig. 1. 
Spec. Char. Transversely elongated, very convex, 
with pointed extremities, radiated, transversely 
and deeply striated ; front elevated, with a 
rounded sinus ; radii obtuse, about 16 on each 
side the central elevation ; beaks a little re- 
moved ; area flat, narrow. 
Full twice as wide as long, nearly semicircular, with 
the sides produced as they approach the extremities of 
the hinge ; the area between the beaks is narrow, with 
nearly parallel edges ; the striae upon the surface are 
regular, and waved by the obtuse radii, which scarcely 
rise enough to be called ribs ; the central elevation is 
obtuse, and occupies the space of about four radii. 
Presented by Professor Sedgwick, who collected it at 
East Thickley, along with Producta calva /3 (tab. 560.). 
