SYRINGOTHYRIS 399 



ternal surface of the cardinal area, including a considerable portion of 

 the delthyrial plate with the syrinx well preserved. This specimen had 

 a very high and flat cardinal area with a narrowly triangular delthyrium, 

 the proportions sc far as preserved being essentially the same as in the 

 type of 8. platypleurus, the only important difference between it and the 

 type of the species, so far as can be seen, is in the apparently perfectly 

 flat external surface of the delthyrial plate, the longitudinal, squarish 

 ridge being absent. 



A small specimen from Louisiana, Missouri, with an approximate width 

 of 28 mm. along the hinge-line, when completed, agrees well with the type 

 of the species in the slope of the cardinal area and in the characters of 

 the delthyrial plate, but the area is proportionally lower and is very 

 slightly arched just under the beak, the number of plications is smaller, 

 which may well be due to the smaller size of the shell, and there are very 

 faint indications of several obscure plications in the mesial sinus. This 

 specimen preserves the minute surface characters which consist of series 

 of minute papilla? arranged in quincunx, giving the surface the peculiar 

 "twilled cloth" appearance so characteristic of the genus, and the punc- 

 tate structure of the shell is indicated. 



Horizon. Burlington limestone. 



SYRINGOTHYRIS TEXTUS (Hall) 

 Plate LXIX, Figs. 6-9 ; Plate LXX, Figs. 1-4 ; Plate LXXI, Figs. 1-2 



1857. Spirifer textus Hall, 10th Kep. N. Y. State Cab. Nat. Hist., p. 169. 

 1875. Spirifer Carteri Meek, Pal. Ohio, vol. 2, p. 285, pi. 14, figs. 7a-d. 

 1881. Spirifer textus White, 2nd Ann. Eep. Dep. Stat. and Geol. Ind., p. 



512, pi. 7, figs. 1-2. 

 1890. Syringothyris texta Schuchert, 9th Ann. Kep. N. Y. State Geol., 



p. 34. 

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



pi. 30, figs. 4-9. 



1894. Syringothyris texta Keyes, Mo. Geol. Surv., vol. 5, p. 88. 



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



26, figs. 9, 12 ; pi. 27, figs. 4-12. 



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

 along the hinge-line, the cardinal extremities angular. The dimensions 

 of a nearly perfect specimen of about average size are : length of pedicle 

 valve from beak to front margin 43.6 mm., length of brachial valve 34.5 

 mm., height of cardinal area 28 mm., width along the hinge-line 95 mm., 

 thickness 43 mm., width of mesial sinus in front 25 mm., width of delthy- 

 rium at hinge-line 18 mm. 



Pedicle valve subpyramidal in form, the surface sloping from the beak 

 to the antero-lateral margins with a gently convex curve, from the beak 

 to the anterior margin along the median line the slope is also gently con- 



