394 MISSISSIPPIAN BRACHIOPODA 



Remarks. This is the smallest of our species of Syringothyris and is 

 characterized by its relatively high and nearly flat cardinal area, whose 

 surface rounds into the lateral slopes of the valve without any sharp line 

 of demarcation. The anterior extension of the dental plates of the 

 pedicle valve to nearly the middle of the valve is another somewhat un- 

 usual character. 



Horizon. Chouteau limestone of the Kinderhook. 



SYRINGOTHYRIS NEWARKENSIS n. sp. 

 Plate LXVIII, Figs. 8-15 



Description. Shell above medium size, greatest width along the hinge- 

 line which is usually greatly extended, the cardinal extremities acutely 

 angular. The dimensions of a partially restored specimen are : length of 

 pedicle valve 31 mm., length of brachial valve 19 mm., greatest width 

 58 mm., thickness 30.5 mm., height of cardinal area 23 mm., width of 

 sinus in front 13 mm., width of delthyrium at base 10 mm. 



Pedicle valve subpyramidal in form, the surface sloping with a gently 

 convex curvature from the umbo to the lateral and anterior margins, or 

 sometimes slightly concave from the umbo to the cardinal extremities; 

 mesial sinus non-plicate, originating at the beak, of moderate width and 

 depth, rounded in the bottom, a little produced in front in a rounded ex- 

 tension; beak pointed, a little incurved; cardinal area high, gently con- 

 cave with the curvature increasing towards the beak, the lateral margins 

 sharply defined, the surface sloping anteriorly from the hinge-line, the 

 lower and flatter portion lying at an angle of about 60 degrees to the 

 plane of the valve; the vertically marked secondary area well defined 

 when the surface of the shell is well preserved, each section at the cardinal 

 margin being about equal to the width of the delthyrium at its base; 

 delthyrium rather narrow, its width at the base being about two-fifths 

 its height. Surface of each lateral slope marked by from 18 to 20 simple, 

 depressed, radiating plications, which originate along the cardinal margin, 

 growing successively smaller towards the cardinal extremities. Inter- 

 nally the dental lamellae extend anteriorly from the beak for somewhat 

 more than one-third the length of the valve ; the delthyrial plate is mod- 

 erately depressed below the surface of the cardinal area and is marked by 

 a distinct longitudinal rib which is produced notably beyond the margin 

 of the plate as a free extension of the syrinx. 



Brachial valve emarginate in front, most convex between the middle 

 and the anterior margin on the median line, the surface curving more ab- 

 ruptly to the cardinal margin, compressed towards the cardinal extremi- 

 ties; mesial fold well developed, originating at the beak, non-plicate, 

 rounded or slightly flattened on top ; beak short and somewhat incurved, 

 projecting a little beyond the cardinal margin. Surface of each lateral 



