354 THE PALEONTOLOGY OF MINNESOTA. 
[Lingulasma galenensis. 
Trimerellide. We do not regard these genera, however, as in the direct line of 
development towards Trimerella, but rather as a branch from Lingula, probably 
having its origin during Trenton times, and terminating with the Niagara forma- 
tion. In the Black River group, at Pauquette Rapids of the Ottawa river, in 
Canada, we find Obolus canadensis, and O. magnificus Billings. These species Billings 
subsequently referred to his genus Obolellina, now regarded as synonymous with 
Dinobolus, Hall. In the Galena formation of Wisconsin and Minnesota, there is 
another form related to the above species, Dinobolus parvus Whitfield. These species 
were in all probability derived from Obolella, while Monomerella and Trimerella had 
their origin in Dinobolus. If this opinion is the proper one, Lingulops and Lingulasma 
should be separated from the Lingulide and Trimerellide, and referred to a new 
family, the Lingulasmatide. This family will then follow the Lingulide. 
LINGULASMA GALENENSIS., 
PLATE XXX, FIGS. 1-4. 
1892, April 1. Lingulasma galenensis W.and S. American Geologist, vol. ix, p. 285. 
Shell large, oblong, subpentagonal. Anterior margin slightly convex, and 
somewhat produced in the center; anterior angles narrowly rounded; lateral margins , 
straight, nearly parallel, rounding rapidly into the more or less convex postero- 
lateral margins. Ventral beak somewhat extended beyond that of the dorsal valve. 
Valves strongly convex, dorsal more than the ventral; point of greatest convexity, in 
the former at one-third the entire length of the valve from the posterior margin, 
in the latter nearly central. Surface of each valve with three slopes in the anterior 
half; the central one flat or very slightly convex, with two broad and shallow depres- 
ssions, causing a small central extension of the anterior margin; lateral sides very 
rapidly descending and somewhat convex. Surface concentrically striated; at irregu- 
lar intervals the strie rise into small pointed pustules radially arranged. These 
radial series of granulations are most prominent on the flattened, central, anterior 
portion of the valves; thirteen to fifteen of them in 5 mm., while twenty-eight 
pustules occupy the same length, measuring along a series. 
Interior of ventral valve with a diamond-shaped coneavo-convex platform, 
strongly elevated, and excavated anteriorly. Posterior margin of the specimen 
slightly broken; an internal arched deltidium not present. Umbonal sear (g) close 
to the posterior broken edge, and upon each side of it is a diverging excavated ridge. 
In front of the umbonal scar, and occupying the lateral portions of the platform, 
are the progressive tracks of the lateral (2) scars. At the posterior end of the plat- 
form are two slightly diverging, linear depressions, which terminate near the mid- 
length of the platform; and here originate two linear and parallel median elevations, 
