230 MISSISSIPPIAN BRACHIOPODA 



tion of the hinge-plate has also been destroyed, this part being distinctly 

 thinner and more delicate than the lateral portions and therefore much 

 more easily destroyed. The continuous hinge-plate has been observed in a 

 sufficient number of individuals, however, to make it certain that that was 

 the normal condition of the species. The punctate structure of the shell 

 is an obscure feature and in many individuals it cannot be detected at all 

 on account of the condition of preservation of the shell. It is occasionally 

 shown, however, and in the specimen in which it is best exhibited the 

 perforations are not distributed uniformly over the entire shell but occur 

 in longitudinal lines, one upon each lateral slope of each plication. This 

 is probably the normal condition towards the beak but it is possible that 

 they become more scattered towards the anterior margin of the shell. 

 Horizon. Hamburg oolite of the Kinderhook. 



RHYNCHOPOBA PUSTULOSA (White) 

 Plate XXIX, Figs. 14-18 ; Plate XXIV, Fig. 82 



1860. Rhynchonella pustulosa, White, Jour. Boston Soc. Nat. Hist., vol. 7, 

 p. 236. 



1894. Rhynchopora pustulosa Hall and Clarke, Int. to Study of Braeh., 



pt. 2, pi. 44, figs. 26-29. 



1895. Rhynchopora pustulosa Hall and Clarke, Pal. N. Y., vol. 8, pt. 2, 



pi. 58, figs. 1-4. 

 1901. Rhynchopcra pustulosa Weller, Trans. St. Louis Acad. Sci., vol. 



11, p. 157, pi. 13, figs. 4-6. 

 1904. Rhynchopora pustulosa Greger, Am. Geol., vol. 33, p. 298-299, 



figs. 10-12. 

 1910. Rhynchopora pustulosa Weller, Bull. Geol. Soc. Am., vol. 21, p 



514, fig. 16. 



Description. Shell below medium size, subpyramidal in form, wider 

 than long, the greatest width near or in front of the mid-length of the 

 shell, the postero-lateral margins a little concave, meeting at the beak in 

 an obtuse angle, the lateral margins rounded, the anterior margin nearly 

 straight or gently convex. The dimensions of a nearly perfect specimen 

 are: length 12.3 mm., width 12.6 mm., thickness 10.3 mm., width of the 

 sinus in front 8.5 mm. 



Pedicle valve convex in the umbonal region with a sigmoidally curved 

 slope to the cardinal margin, to the antero-lateral margin the surface is 

 gently convex and from the beak to the front margin along the median 

 line it is strongly arched in nearly a semicircle ; the mesial sinus is obsolete 

 in the posterior half of the valve, it originates near or in front of the 

 middle of the valve as a broad, shallow, flattened depression and continues 

 as such to the anterior margin, anteriorly it is produced in a broad, 

 lingual extension rounded in front with a serrate margin, whose surface 

 in front lies in nearly a right angle to the plane of the valve; the beak 

 large, moderately incurved, perforated by a large, subcircular foramen; 



