PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 833 
est slopes at the anterior. Palintrope and pseudodeltidium short ; apical foramen 
smaller than usual in the genus. 
Brachial valve fitting closely into the pedicle valve and with concave umbonal 
region ; valve flattened slightly in the vicinity of the cardinal extremities. Most 
concave in the midregion, less so laterally of the middle. 
Pedicle valve with small wide teeth that have deep fossettes, dental plates 
nearly obsolete; muscle area slightly wider than long ; diductor scars large, ad- 
ductor field narrowly elliptical, periphery of muscle field slightly thickened and 
surrounding shell surface tuberculate. 
Brachial valve with notothyrial platform thickened and bearing 2 short shafted 
processes with flattened myophore surfaces. Brachial processes flat, short, sup- 
ported by the notothyrial platform. Median ridge nearly obsolete. Posterior 
adductor scars the larger; anterior adductor processes long and convex inward. 
Entire inner surface of visceral portion strongly tuberculate. 
Measurements in mm.— 
Brachial Hinge Surface 
Length length Width width Thickness length 
ET OIGHUIE s faheisyn ss orete's 16.5 14.5 18.3 18 + 3.4 20.5 
Paratype (117595).. 17.9 13.8 22.2 20.6 4.8 22+ 
Types.—Holotype: 1175941; figured paratypes: 117594c,d,h, 117595, 117596; 
unfigured paratypes: 117594a,b,e-g. 
Horizon and locality Lincolnshire formation (2-foot layer on marble) in 
Tennessee: In Clinch Valley at Shiloh Church, near center of the northwest 
subquad. of Pressmans Home (T.V.A. 171-NE) Quadrangle. 
Same formation in Virginia: At Marcem Quarry, 2 miles west of Gate City, 
Gate City (T.V.A. 188-NE) Quadrangle. 
Arline formation in Virginia: In Porterfield Quarry, 5 miles east of Saltville, 
Maccrady (T.V.A. 218-NW) Quadrangle. 
Discussion.—This species is a moderately large one characterized by a subrec- 
tangular to subquadrate outline, gently convex visceral region, moderately strong 
geniculation, and moderately deep brachial valve. It differs from D. obtusa in 
not having a wide hinge, in the more narrowly rounded anterior, the less deep 
brachial valve, and a less obtuse angle of geniculation. It differs from D. prona 
which also occurs in the Lincolnshire formation in its less abrupt geniculation 
and the longer and more gently inclined trail. 
DACTYLOGONIA PALUSTRIS (Willard) 
Leptaena palustris WiLtLarp, Bull. Mus. Comp. Zool., Harvard Coll., vol. 68, No. 6, p. 278, 
pl. 3, fig. 14, 1928. 
Type.—Holotype: M.C.Z. 86109. 
Horizon and locality.—Holston limestone= Farragut formation in Tennessee: 
At Concord, Concord (T.V.A. 138-SW) Quadrangle. 
Discussion.—This is a small species characterized by fairly regular form, mod- 
erate geniculation, and a moderately but irregularly wrinkled visceral region. No 
specimens in the National Collection can be identified with this species. 
