PART, J CHAZYAN AND RELATED BRACHIOPODS—-COOPER 665 
Same formation in Vermont: At Isle LaMotte, Rouses Point (15’) Quad- 
rangle; near Fort Cassin, Port Henry (15’) Quadrangle. 
Discussion.—This species is characterized by strong, somewhat distant costae, 
deep sulcus, and prominent median costa. It is similar to S. cuneata, but that 
species is more deeply sulcate, narrower, and more strongly costate. Its orna- 
mentation is arranged on a different pattern with 5 costae forming the fold. 
SPHENOTRETA CUNEATA Cooper, new species 
Plate 124, 1, figures 46-54 
Shell small, elongate triangular in outline; sides nearly straight and forming 
an apical angle of 65°; anterolateral extremities narrowly rounded; anterior 
margin broadly rounded ; widest at the front; anterior commissure sulcate ; sur- 
face with about 12 rounded to subangular costae, 4 of which occupy the sulcus. 
Pedicle valve gently convex in lateral profile, broadly convex in anterior pro- 
file. Umbonal region narrowly swollen. Median costa larger than all the others 
and extending from umbo to anterior margin as a high ridge. Median costa with 
2 depressed costae on each side forming a fascicle corresponding to the median 
fold and opposing the 4 costae of the sulcus of the brachial valve. Flanks slightly 
elevated above the fold but not above the median costa; flanks narrow and 
marked by about 3 costae. 
Brachial valve moderately convex in lateral profile, more convex than the 
pedicle valve; anterior profile deeply sulcate and with precipitous lateral slopes. 
Umbo sulcate; sulcus widening and deepening anteriorly to the front margin 
where it occupies about three-fifths the width. Median slopes long and steep to 
the bottom of the subangular sulcus, each slope occupied by 2 costae. Flanks 
narrowly rounded. 
Measurements in mm.— 
Brachial Greatest 
Length length Midwidth width Thickness 
PA UOER EH oiela aisles Weraas tei dia oon 3.8 3.5 22 2.8 igs 
Paratype (pedicle valve 117189b). 4.8 ? a3 4.3 1.2? 
a (brachial valve 117180c) ? 4.5 3.0 3.9 ? 
af ‘ Oeiiees rT EEF TOOR) r 4.6 3.6 4.8 0.9? 
Types.—Holotype: 117189a; figured paratypes: 117189b-d,g ; unfigured para- 
types: 117189e,f. 
Horizon and locality.—Sevier formation in Tennessee: Above the old marble 
quarry 4 mile southeast of Hambright Mine, 8 miles south of Cleveland ; 1.3 miles 
south of the center of Athens, Athens (T.V.A. 125-NE) Quadrangle. 
Discussion.—This species is characterized by its strong costae and the great 
depth and angularity of the sulcus. It is similar to S, acutirostra but differs in 
having the pedicle fold composed of 5 costae rather than 3, in having a deeper 
sulcus, and a less rounded brachial valve. 
