176 MISSISSIPPIAN BRACHIOPODA 



plications usually nearly obsolete upon the lateral slopes of the valves. 

 Paryphorhynchus also is a much larger shell with the entire external 

 surface of the valves marked by fine radiating striae in addition to the 

 plications, and Pugnoides has the plications becoming obsolete towards 

 the beak. 



CAMAROTCECHIA CHOUTEAUENSIS Weller 

 Plate XXIV, Figs. 34-40 



1910. Camarotcechia choutea-uensis Weller, Bull. Geol. Soc. Am., vol. 21, 

 p. 510, fig. 10. 



Description. Shell small and thick, triangularly subovate in outline, 

 wider than long, the greatest width near or in front of the middle, the 

 postero-lateral margins meeting at the beak in an obtuse angle, the 

 lateral margins rounded, the anterior margin gently convex. The dimen- 

 sions of two nearly perfect specimens are : length 11 mm. and 9.3 mm., 

 width 11.5 mm. and 10 mm., thickness 10 mm. and 8 mm., width of sinus in 

 front 7 mm. and 5.6 mm. 



Pedicle valve shallow, narrowly convex on the umbo, the surface sloping 

 from the umbo to the cardinal margin, at first with an abrupt convex 

 curvature, becoming gently concave as it approaches the margin, towards 

 the antero-lateral margins the surface is gently convex and from the 

 beak to the front along the median line it is strongly and nearly regularly 

 arched; the mesial sinus originates near the mid-length of the shell, it is 

 abruptly depressed, its surface is nearly straight or slightly convex 

 transversely across the bottom and is strongly curved towards the oppo- 

 site valve longitudinally, anteriorly it is produced into a broad, elongate, 

 lingual extension which lies in nearly a right angle to the plane of the 

 valve, its greatest width is equal to about one-half the total width of the 

 valve; the beak is small and moderately incurved; the delthyrium is 

 nearly filled by the beak of the other valve, the deltidial plates and 

 foramen are obscure and have not been observed in the specimens 

 studied; the plications are sharply angular and originate at the beak, 

 three or four occupy the bottom of the sinus, these being a little less 

 angular than those upon the lateral' slopes, each lateral slope bears from 

 six to eight plications which become successively fainter towards the 



O 



FIG. 5. A series of eight cross-sections of the rostral portion of the shell of 

 Camarotcechia chouteauensis (X 2%), showing the characters of the median 

 septum, crural cavity, hinge-plate, and crura of the brachial valve, and the 

 dental lamellae of the pedicle valve. 



