862 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Pedicle valve moderately convex in lateral profile and with the maximum 
convexity in the umbonal region; anterior profile broadly convex with moder- 
ately steep sides ; umbo swollen posterior to the posterior margin ; median region 
strongly swollen; posterolateral areas slightly auriculate; posterolateral slopes 
steep; anterior slope moderately steep. Interarea long. Interior unknown. 
Brachial valve broadly concave, greatest concavity near the middle; sides not 
strongly incurved. Interior with prominent septal ridges ; adductor field marked 
by transverse plates uniting the septa about one-third the length from the beak; 
cardinal process small; chilidium short. 
Measurements in mm.— 
Brachial Hinge Thick- 
Length length Midwidth width ness Height 
Holotype | buys wi seh 13.0 ? 12.9 9.8 iy 4.1 
Paratype (1110IIa)... I1.0 ? 10.4 10.2 ? 3.6 
i (11 T0004), 2 ce ? 12.4 12.4 10.1 ? ? 
Types——Holotype: 111011b; figured paratypes: 111004, I11007, IIIOIIa, 
117573, 117574; figured specimen: 117575. 
Horizon and locality—Edinburg formation (Cyrtonotella zone) in Stras- 
burg (15’) Quadrangle, Virginia: Small glen at the switch about 3 mile east of 
Strasburg Junction; quarry 4 mile east of the railroad station at Strasburg 
Junction ; south side of the road 0.2 mile east of Strasburg Junction ; Edinburg 
formation, 14 miles south of Wadesville, Winchester (15’) Quadrangle. 
Edinburg formation (Nidulites zone) in Strasburg (15’) Quadrangle, Vir- 
ginia: 100 yards south of the Battlefield Crystal Caverns entrance on U. S. high- 
way 11, Hupp Hill, 1 mile north of Strasburg; along Tumbling Run, 14 miles 
southwest of Strasburg. 
Little Oak formation in Alabama: 4 mile north of the bridge on U. S. High- 
way 31, Pelham, Bessemer Iron District (15’) Quadrangle. 
Discussion.—This species is distinguished from the others described herein by 
its quadrate form and generally low convexity. The brachial valve is similar to 
that of C. trentonensis in its low convexity, but it is a wider species than the 
Rysedorf one. Christiania platys is quite unlike either C. tenwicincta (McCoy) 
or C. oblonga (Pander). 
CHRISTIANIA SUBQUADRATA (Hall) 
Plate 214, C, figures 6-8; plate 214, D, figures 9-39; plate 215, C, figures 11, 12; 
plate 215, E, figures 14-19; plate 221, B, figures 7-15 
Leptaena subquadrata Hatt, 2d Ann. Rep., New York State Geol., pl. 46, figs. 32, 33, 1883. 
Christiania subquadrata (Hall) Hatt and CLarKkE, Pal. New York, vol. 8, pt. 1, pp. 298, 351, 
pl. 15, figs. 32, 33; plate 15A, fig. 36; pl. 20, figs. 18-20, 1892; 48th Ann. Rep. New York 
State Mus., vol. 2, p. 351, pl. 6, figs. 13-18, 1895; 14th Ann. Rep. New York State Geol. 
for 1894, p. 351, pl. 6, figs. 13-18, 1897. 
Christiania trentonensis Butts (not Ruedemann), Alabama Geol. Surv., Special Rep. 14, 
p. 116, pl. 26, figs. 22-24, 1926. 
Variable, attaining a length of about 4 inch; elongate oval to longitudinally 
subrectangular; sides subparallel to slightly divergent; anterior margin nar- 
