SYRINGOTHYRIS 395 



slope marked by simple, depressed, rounded, radiating plications, similar 

 in number to those of the opposite valve, but marked off by more strongly 

 impressed radiating furrows. 



The minute surface markings of the shell are not well preserved upon 

 any specimen observed, but the characteristic markings of the genus are 

 suggested at several points, and the punctate structure of the shell is 

 clearly shown. 



Remarks. This species is perhaps most closely related to 8. typo,, but 

 it is a smaller shell, more extended along its cardinal line in its normal 

 condition, with relatively much shorter brachial valve which is much 

 more compressed towards the cardinal extremities. In the pedicle valve 

 the delthyrium is much more narrowly triangular than in 8. typa, and the 

 mesial sinus is narrower. One specimen studied is less extended along 

 the hinge-line than usual, and has more nearly the form of S. typa, but it 

 is a distorted example, showing that it must have lived under abnormal 

 conditions, but even this specimen has a much more narrowly triangular 

 delthyrium and is more compressed towards the cardinal extremities of 

 the brachial valve than 8. typa. Two other species of the genus which 

 have essentially the same angle of divergence between the cardinal area 

 and the plane of the valve, are 8. hannibalensis and 8. halli, but each of 

 these species has a proportionally lower cardinal area and a more broadly 

 triangular delthyrium. 



Horizon. Kinderhook. 



SYRINGOTHYRIS TYPUS "Winchell 

 Plate LXIX, Figs. 1-5 



1863. Syringothyris typa Winchell, Proc. Acad. Nat. Sci. Phil., p. 7. 

 1886. Syringothyris typus Winchell, Geological Studies or Elements of 



Geology, p. 236, figs. 181-182. 

 1890. Syringothyris Carteri Schuchert, 9th Ann. Rep. N. Y. State Geol., 



p. 30 (in part). 



1894. Syringothyris typa Hall and Clarke, Int. to Study of Brach., pt. 2, 



pi. 30, figs. 1-2. 



1895. Syringothyris typa Hall and Clarke, Pal. N. Y., vol. 8, pt. 2, pi. 26. 



figs. 6, 7, 10 ; pi. 27, figs. 1-3. 



Description. Shell large, broader than long, the greatest width along 

 the hinge-line, the cardinal extremities angular. The dimensions of a 

 nearly complete but somewhat distorted specimen are : length of pedicle 

 valve from beak to front 47 mm., length of brachial valve, approximately 

 40 mm., width along hinge-line 68.5 mm., height of cardinal area 26 mm., 

 thickness approximately 42 mm., width of sinus in front 28 mm., width 

 of delthyrium at base 16 mm. 



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

 convex curvature from the umbo to the lateral and anterior margins; 

 mesial sinus non-plicate, originating at the beak where it is rather well 



