190 MISSISSIPPIAN BRACHIOPODA 



and produced in front in a broad, rounded, lingual extension whose sur- 

 face at the front of adult shells lies in nearly a, right angle to the plane of 

 the valve ; beak small, pointed, incurved so as to be almost in contact with 

 the umbo of the opposite valve in full grown specimens, pierced at the 

 apex by a very small subcircular foramen ; delthyrium broadly triangular, 

 nearly filled by the beak of the opposite valve, the deltidial plates incon- 

 spicuous; plications coarse and strong, rounded, with furrows of about 

 equal width between, three or four plications are usually present in the 

 bottom of the broad sinus and three or four upon each lateral slope, mak- 

 ing from nine to twelve upon the entire valve, the one nearest the postero- 

 lateral margin on each side usually being faint or obscure. Internally 

 the teeth are supported by a pair of dental lamella?- which diverge ante- 

 riorly and continue for about one-fifth of the length of the valve. 



Brachial valve much more convex than the pedicle, the greatest depth 

 at or near the anterior margin, the surface sloping with a gradually in- 

 creasing curvature from the anterior margin to the beak, from the median 

 line the surface curves abruptly to the postero-lateral margins and towards 

 the beak is sometimes a little inflected as it approaches the margin to 

 form, with a similar inflected portion of the opposite valve, an ill-defined, 

 slightly concave, lateral area on each side of the valve, in the anterior 

 portion of the valve the surface passes from the median line with an ab- 

 rupt double curvature, first to the border of the mesial fold and then to 

 the lateral margins of the valve; the mesial fold is ill-defined posteriorly 

 but originates back of the middle of the valve and is strongly elevated in 

 front where it is broad and rounded on top ; the beak is strongly incurved 

 beneath that of the opposite valve, the plications correspond in form and 

 number to those of the opposite valve with which they alternate. Inter- 

 nally there is no cardinal process and the hinge-plate is divided to the 

 base, being supported in its initial portion by a median septum which di- 

 vides to form a crural cavity between the two divisions of the hinge-plate 

 as in the genus Canw^rotoechia. 



In addition to the plications the surface of both valves is marked by 

 fine, radiating, longitudinal striae, about four or five of which occupy the 

 space of one millimeter and by fine concentric lines of growth. On some 

 examples stronger lines of growth are sometimes present at intervals. 



Remarks. This species can be easily distinguished from the other mem- 

 beers of the genus Paryphorhynchus, by its smaller size and somewhat in- 

 termediate character, it being distinctly shorter than P. elongatum and 

 narrower than P. transversum*. The species occurs most commonly in bed 

 No. 4 of the Kinderhook section at Burlington, Iowa, and in a Kinderhook 

 limestone near Kinderhook' Pike County, Illinois. The recorded occur- 

 rence of the species in the Louisiana limestone of Missouri is probably an 

 error. 



Horizon. Kinderhook. 



