824 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
The most striking feature of this peculiar genus is the median septum which 
is unlike that of any other leptaenoid. This originates just inside the space be- 
tween the anterior ends of the adductor blades and extends anteriorly nearly to 
the front margin. At its posterior end the septum is stout and descends into the 
adductor field as a sort of muscle platform. Anteriorly the septum is so strongly 
elevated that it divides that part of the valve into 2 chambers. The trace of this 
high-bladed septum can be seen on the pedicle side of the steinkern figured on 
plate 225, B, figure 7. An impression of the blade is shown in figure 18 of the 
same plate. 
Teratelasma differs from Dactylogonia in its exterior form which is not leptae- 
noid and in the arrangement of the adductor processes and the presence of the 
high median septum. 
TERATELASMA NEUMANI Cooper, new species 
Plate 225, B, figures 5-23 
Shell small, subquadrate in outline, with the hinge equal to the greatest width ; 
cardinal extremities nearly a right angle; sides nearly straight; anterior margin 
somewhat narrowly rounded; anterior commissure narrowly sulcate; surface 
finely costellate, about 8 crowded in the space of I mm. 
Pedicle valve nearly flat in lateral profile ; narrowly keeled medianly and with 
the sides somewhat concave in anterior profile; umbo narrowly swollen, the 
swelling continued anteriorly to form a narrow, subcarinate fold that extends to 
the front margin; sides of fold steep; flanks bounding fold flattened to concave; 
interarea moderately long, apsacline. 
Brachial valve gently convex to nearly flat in lateral profile; anterior profile 
broadly and very gently convex and with the median region narrowly depressed ; 
sulcus originating at the umbo and extending to the front margin where it occu- 
pies about one-quarter the width; flanks bounding sulcus gently convex. 
Measurements in mm.— 
Brachial Hinge 
Length length Midwidth width Thickness 
Paratype (pedicle valve 117938f) ..... 6.8 i? 9.0 10.0 ? ? 
oy (brachial valve 117938j).... ? 5.3 7.9? 8.6 ? 
Types.—Holotype: 117938d; figured paratypes: 117938c,e-g,j,k,l-o,q; un- 
figured paratypes: 117938a,b,h,i,p. 
Horizon and locality.—Sevier formation (Benbolt equivalent) in Tennessee: 
0.53 mile east-southeast of Old Kagley Church, Binfield (T.V.A. 139-NE) 
Quadrangle. 
Discussion—No other species of this genus is known to which this one 
may be compared. The only known specimens are from the Sevier formation 
at the Benbolt level. 
DACTYLOGONIA Ulrich and Cooper, 1942 
Dactylogoma Uxricu and Cooper, Journ. Paleont., vol. 16, No. 5, p. 623, 1942. 
Shell of moderate size often attaining a little more than an inch in width, usu- 
ally wider than long, with the hinge forming the widest part; lateral margins 
