416 
PALAEONTOLOGY OF NEW YORK. 
forms are usually longer than wide, the Western ones are as long as wide, and 
sometimes wider, and the cardinal extremities are usually extended and frequently 
mucronate. They are likewise less ventricose, the space between the valves being 
less, and the muscular impressions not so strongly marked. In these respects, 
however, the New York specimens of the Chemung group more nearly resemble 
the Western ones. 
Geological formation and locality. In rocks of the age of the Hamilton group, 
at Rock Island, Ill., and at Independence and New Buffalo, Iowa. 
Spirifera mala. 
PLATE LXIII, FIGS. 6-13. 
Mhyris maia: Billings. Canadian Jour. Ind. Sci. and Arts, May, 1860, p. 276. 
Shell below the medium generic size, ventricose, with rounded cardinal 
angles, giving a longitudinally ovate outline, with a depressed suhglobose 
form ; hinge line very short; cardinal area narrow and sometimes hidden 
by the beak. 
Dorsal valve suborbicular, moderately ventricose, with a distinctly elevated 
rounded mesial fold. 
Ventral valve more ventricose than the opposite,' with a large, tumid ? 
incurved beak, and a moderate, subangular mesial sinus. 
Surface destitute of plications, but marked by more or less distinct concen¬ 
tric striae of growth. 
This species is of the type of, and in some conditions greatly resembles, S. lineata, 
of the Coal measures, but differs in the projecting beak and more ventricose dorsal 
valve, as also in the surface markings. It is also very similar to tS. subumbona , 
of the Marcellus shale, but is a larger form, and differs in the shorter hinge line, 
larger beak and more ventricose dorsal valve, and in the surface markings. 
Geological formation and locality. In the Corniferous limestone of Ohio and 
Canada West. The specimens figured are from Rev. H. Herzer, of Columbus, Ohio. 
