PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 829 
lation variable; surface marked by strong and fine costellae, about 5 of the 
latter in 5 mm. at the front margin and about 7 fine costellae separating the 
larger ones. Fine costellae strongly cancellated by fine concentric lines. 
Pedicle valve with variable lateral profile, the visceral portion varying from 
flat to gently convex, the geniculated part from narrowly convex. Trail nearly 
flat to gently convex and varying in angle of geniculation from 60° to 100°. 
Geniculation occurring 6 or 7 mm. anterior to the beak. Geniculated part nar- 
rowly to roundly convex depending on angle of geniculation. Umbonal and 
median regions somewhat swollen; flanks of visceral part somewhat depressed. 
Interarea moderately long; pseudodeltidium large and convex. 
Brachial valve with visceral part gently concave, with the median region the 
deepest part and the flanks somewhat flattened. Trail moderately long, slightly 
concave ; adductor plates strongly developed. 
Measurements in mm.— 
Brachial Mid- Hinge Thick- Surface ‘Trail 
Length length width width ness. length length 
Hypotype (117580a)..........-. 10.8 8.8 16.4 15.6+ 4.1 18.0 9.0 
4 (GREZE OU) sia hesentve eocege' 10.8 9.1 14.6 ? 4.2 16.0 8.0 
rk (Carnegie Mus. 5446). 11.7 ? 16.0 21.7 iP 15.0 7.0 
Types.—Figured hypotypes: Carnegie Mus. 5446; A.M.N.H. 25049/1,2,3; 
U.S.N.M. 117589a-c, 117590a, 117593a,b. 
Horizon and locality—Crown Point formation in New York: At Sloop Bay, 
Valcour Island, Lake Champlain, Plattsburg (15’) Quadrangle. 
Same formation in Vermont: On Isle La Motte, Rouses Point (15’) Quad- 
rangle ; on a small peninsula of the west shore of Providence Island, Plattsburg 
(15’) Quadrangle; Fort Cassin, Port Henry (15’) Quadrangle. 
Discussion.—This species is without doubt a fairly variable one, but in spite 
of that it does not seem to occur in the Southern Appalachians. Dactylogonia 
alternata has been mistaken for it but that species is larger and less strongly 
geniculated. Dactylogomia incrassata has been confused on Mingan Island with 
a somewhat more robust form having a more elongate interarea and longer trail. 
The two species of Dactylogonia now known from Oklahoma are quite unlike 
D. incrassata because they are only slightly geniculated. Dactylogonia marmorata 
is suggestive but that species has fairly prominent wrinkles which distinguish 
it at once from the New York species. 
DACTYLOGONIA MAGNA Cooper, new species 
Plate 194, E, figures 28-30; plate 220, C, figures 9-17 
Shell large for the genus, slightly wider than long with the hinge not quite 
equal to the shell width at the middle; sides and anterior margin gently rounded ; 
point of geniculation about 12 mm. anterior to the beak; angle of geniculation 
about 95°. Ornamentation consisting of a few strong costellae in a field of finer 
ones ; 3 strong costellae to 5 mm. at the front margin; strong costellae separated 
by as many as 10 of the finer kind; fine costellae cancellated by fine concentric 
lines. Posterior margin with short vertical wrinkles. 
