308 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Umbo gently swollen, the swelling continuing anterior to the front margin as a 
broad, poorly defined fold. Lateral slopes long and gentle; umbonal slopes fairly 
steep. Pedicle interior with short, stout dental plates, small teeth, and subquad- 
rate muscle field. Pallial marks not preserved. 
Brachial valve gently convex in lateral profile, broadly convex in anterior pro- 
file, but with the median region sulcate and the sides appearing as two low swell- 
ings. Umbo gently swollen; sulcus originating on the umbo, extending anteriorly 
to the front margin. Sulcus narrow throughout, deepest in the median region and 
becoming broad and shallow at the anterior margin. Flanks gently swollen with 
short, steep slopes to the sulcus but long and gentle slopes to the margins. Bra- 
chial interior with small shallow notothyrial cavity, thick notothyrial platform, 
short brachiophores, short median ridge and simple cardinal process stoutest at 
the anterior end. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Holotype gacisid:. .padlievgwermee 18.9 ? 25.6 27.4 ? 
Paratype (pedicle valve 116874a)... 17.6 ? 25.8 29.0 4.0 
COs ee  MELOSTAC nee 7ek ? 23.4 25.4 4.1 
y (brachial valve 116874d).. ? 20.8 26.6 28.4 2.6 
a Oe Ac) PROSTAR eo aw 17.7 19.7 23.4 aia ¥ 
Types.—Holotype: 116874e ; figured paratypes: 116874b,d,h,l,n,o,q ; unfigured 
paratypes: 116874 a,c,f,g,i-k,m,p. 
Horizon and locality—Tellico formation (sandstone No. 3 of Neuman) in 
Tennessee: 0.3 mile northwest of Cold Springs School, Wildwood (T.V.A. 
147-SE) Quadrangle. 
Discussion —This is one of the largest Orthambonites so far seen in the Ordo- 
vician of the Appalachians. It is characterized by its squarish muscle area in 
the pedicle valve, the short brachiophores and the strong costae. It strongly re- 
sembles Dinorthis and may be mistaken for that genus. The strongly convex ped- 
icle valve, however, should eliminate the confusion. Of described species O. neu- 
mani is most like O. dinorthoides. It differs in having more numerous costae, 
larger size, and a squarer muscle field in the pedicle valve. This species differs 
from O. brachiophorus, which it externally resembles, in having much shorter 
brachiophores and a squarish muscle field in the pedicle valve. 
ORTHAMBONITES OCCIDENTALIS Cooper, new species 
Plate 34, B, figures 7-9 
Shell of about medium size for the genus, the length about five-sixths the width. 
Hinge slightly narrower than the greatest shell width which is at about the mid- 
dle. Cardinal extremities slightly obtuse. Sides slightly rounded; anterior mar- 
gin broadly rounded. Surface marked by 27 elevated, narrowly rounded, slen- 
der costae separated by spaces about equal to the costae in width. 
Pedicle valve moderately convex in lateral profile with the greatest convexity 
at about the middle; anterior profile strongly convex with broadly rounded crest 
