400 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Shippensburg formation (Pinesburg member) in Maryland: At Wilson on 
U. S. Highway 40, west side Conococheague Creek, 7 miles west of Hagerstown, 
Williamsport (15’) Quadrangle. 
Shippensburg formation (Pinesburg member) in Pennsylvania: In field on 
north side of railroad, 2} miles southwest of Marion, Chambersburg (15’) 
Quadrangle. 
Sevier formation (sandstone No. 5 of Neuman) in Tennessee: 0.57 mile 
southwest of Rock Branch, Kinzel Springs (T.V.A. 148-NE) Quadrangle. 
Discussion.—In general this species is characterized by its transverse form in 
most of the examples observed and by the bifurcation of the ribs particularly on 
the flanks. Dinorthis quadriplicata is regarded as a synonym of D. transversa, 
perhaps as one end member of a variable species. The type specimen of D. quad- 
riplicata differs from the average specimen of D. transversa in being less wide 
proportionately and in having the median costae strong and unbifurcated. Many 
specimens in the collection are intermediate between this form and the type of 
D. transversa, which is quite wide and in which the median costae show some 
bifurcation. As most of the specimens lie between these two extremes it is be- 
lieved D. transversa and D. quadriplicata belong to the same species. 
The species is a very variable one showing extremes of ornamentation as well 
as of outline. The costae of the flanks in general always show some bifurcation. 
The large costae of the median region of both valves may or may not show 
bifurcation, but more specimens do show it than not. 
DINORTHIS TRANSVERSOIDES Cooper, new species 
Plate 61, FE, figures 23-28 
Small, attaining about half the size of D. transversa which it resembles ; pedicle 
valve nearly flat in lateral profile but with the umbonal region slightly swollen ; 
anterior profile nearly flat; sides rounded, anterior margin truncated; median 
region nearly flat; anteromedian area gently sulcate and occupied by a fascicle 
of costae larger than those on the bounding areas; flanks very gently convex; 
posterolateral areas deflected slightly toward the brachial valve. 
Brachial valve strongly convex in lateral profile with the greatest convexity 
in the median region; anterior and posterior slopes steep and nearly equal in 
length ; anterior profile strongly convex; umbo sulcate, sulcus originating at the 
beak and extending to the anterior margin, narrow and shallow throughout its 
length ; flanks bounding sulcus and lateral slopes inflated ; posterolateral extremi- 
ties swollen. 
Measurements in mn.— 
Brachial Hinge 
Length length Width width Thickness 
Holotype (pedicle valve) ............ 2.7. ? 16.0 12.9 ? 
Paratype ( “ 4 DLOSATA) ec cre 12.6 ? 17.5 15.2 ? 
i (brachial valve 11034Ic)....  ? 13.0 16.3 12.4 a7. 
pA, Aaa ty inal Foal ie 12.6 16.2 12.7 3.9 
