232 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Discussion.—The specimens available for study are not very well preserved. 
The U. S. National Museum specimens are thin shelled and probably young 
forms. This may account for the small development of the muscle platforms. 
This species is proportionally wider than long and thus contrasts strongly with 
O. canadensis which is the reverse. 
OBOLELLINA PARVA (Whitfield) 
Dinobolus ? parvus WHITFIELD, Geol. Wisconsin, vol. 4, pl. 27, figs. 8-10, 1882—WINCHELL 
and SCHUCHERT, Geol. Minnesota, vol. 3, p. 356, fig. 27, 1803. 
This interesting species differs strongly from O. dixonensis particularly in 
details of the brachial valve. Obolellina parva has a fairly strongly developed 
and prominent median ridge extending anterior to the muscle platform. A trace 
of a median ridge is also present in the opposite valve. An impression of the 
brachial interior (45548a) shows a depression bounded by 2 short, low ridges, 
but the significance of this structure is not at once evident. It may be a depres- 
sion similar to that in the brachial umbo of O. magnifica. 
Types.—Holotype in the form of wax impressions of the two valves: 45548a,b. 
Horizon and locality.—Prosser formation (Fusispira bed), Wykoff, Minn. 
Family LINGULASMATIDAE Winchell and Schuchert, 1803 
Linguoidal, corneous brachiopods with large internal platforms. 
Genus LINGULASMA Ulrich, 1899 
Lingulasma Utricu, Amer. Geol., vol. 3, p. 383, 1880. 
Most of the species of this genus found in lower Middle Ordovician rocks are 
generally imperfect. Many of the occurrences are found in vertical position in 
the rock, with the beak and platform regions badly crushed. As a consequence 
the apical region of both valves and the nature of the platforms of most species is 
still unknown. The character of the ornamentation with its rows of pustules or 
elevated dashes is generally very distinctive, and the variety of ornament makes 
specific splits possible on only small sections of the shell. 
LINGULASMA COMPACTUM Cooper, new species 
Plate 12, F, figures 18-21 
Shell longer than wide, with subparallel sides and somewhat narrowly rounded 
anterior margin. Valves subequal in depth. Traces of platforms visible in 
crushed posterior third. Ornamentation distinctive, consisting of strong con- 
centric undulations of growth; surface of sides and flanks covered by crowded, 
rounded, minute, wavy concentric lines but on body of shell in the median re- 
gion the concentric elements become minutely discontinuous, the concentric 
ridges bearing granules arranged in radial rows. Radial elements only poorly 
developed on the flanks and along the margins, but on the median region the 
rows are closely crowded, about 7 in the space of a millimeter. 
