l ss MISSISSIPPIAN BRACHIOPOUA 



PARYPHORHYNCHUS TRANSVERSUM Weller 

 Plate XXVI, Figs. 23-28 



1895. Pugnax missouriensis Hall and Clarke, Pal. N. Y., vol. 8, pt. 2, pi. 62, 

 figs. 44-45. (Not Rliynclionella missouriensis Shumard, 1855.) 



1900. Pugnax striatocostata, var. ? Weller, Trans. St. Louis Acad. Sci., 

 vol. 10, p. 72, pi. 2, figs. 16-17. 



1905. ParaphorJiynchus transversum Weller, Trans. St. Louis Acad. Sci., 

 vol. 15, p. 264, pi. 1, figs. 12-15. 



Description. Shell of medium size, wider than long, transversely 

 subelliptical in outline, the greatest width near the mid-length, the pos- 

 tero-lateral margins nearly straight and meeting at the beak in an obtuse 

 angle, the lateral and antero-lateral margins rounded, the anterior mar- 

 gin gently convex. The dimensions of a nearly complete internal cast 

 are: length 25 mm., width 31 mm., thickness 23 mm., width of sinus in 

 front 19.5 mm. 



Pedicle valve flattened back of the umbo, the surface curving rather 

 abruptly to the postero-lateral margin and usually incurved to some ex- 

 tent, to the antero-lateral margins the surface is gently convex, and to 

 the front it is strongly arched; the mesial sinus originates in or near 

 the umbonal region , and becomes rapidly deeper towards the front ; it is 

 deeply concave anteriorly and is produced in a rounded lingual extension 

 in front; the beak is obtusely pointed and rather sharply incurved; the 

 plications are broad, subangular or rounded on top with furrows of about 

 equal width separating them, three or more, usually four, are included 

 in the sinus with about four upon each lateral slope of the valve, some- 

 times the lateral plications of the sinus become obsolete towards the front. 

 Internally the teeth are supported by a pair of diverging dental lamellae 

 which extend anteriorly from the beak for about one-fourth the length 

 of the valve. 



Brachial valve much more convex than the pedicle, the greatest con- 

 vexity at or near the anterior margin, the surface sloping from the front 

 to the beak along the median line with a gradually increasing curvature, 

 posteriorly the surface curves abruptly towards the postero-lateral mar- 

 gins and is slightly inflected, forming with the narrower incurved por- 

 tion of the opposite valve a lateral concave region on each side of the 

 beak ; mesial fold not differentiated in the umbonal region, at first 

 gradually and then more strongly elevated towards the front, convex on 

 top with rather steep sides, its width in front equal to nearly half the 

 width of the shell ; the lateral slopes curving strongly towards the oppo- 

 site valve both laterally and anteriorly; the beak strongly incurved 

 beneath that of the opposite valve ; the plications are similar in form and 

 number to those of the opposite valve, sometimes the two lateral plications 

 of the fold coalesce with the next inner ones towards the front. Internally 



