BRACHIOPODA. 367 



gradually to the lateral margins, and abruptly to the front, forming a broad and 

 deep sinus, which is sharply defined at the sides, and bears from two to four 

 angular plications. Two or more smaller plications occur on each lateral slope. 



The brachial valve is well rounded in the umbonal region, but the median 

 fold is defined only near the anterior margin. It bears from three to five pli- 

 cations, with three on e:ich lateral slope. All the plications, as well as fold and 

 sinus, become obsolete in the umbonal region, and in old and thickened shells 

 the latter can be distinguished only at the anterior margins of the valves. In 

 the interior there is a supported spondylium in the pedicle-valve, but in the 

 brachial valve the septal plates do not unite. 



Hudson River group. Wilmington, Illinois. 



Parastrophia Greenii, sp. nov. 



PLATE LXIII, FIGS. 17-20, 22. 



Shell robust, with convex brachial valve and shallow pedicle-valve, convex 

 in the umbonal region, but concave anteriorly. Beaks not prominent ; that of 

 the pedicle-valve low but erect ; that of the brachial valve full and incurved. 

 Cardinal slopes sharply defined on pedicle-valve. Median fold and sinus on 

 brachial and pedicle-valves not stronglyjdefined except at the anterior margin. 

 The brachial valve bears six broadly rounded plications which are obsolete in 

 the umbonal region ; four of these belong to the median fold, the other two to 

 the lateral slopes. The pedicle-valve has five plications, with three in the me- 

 dian sinus. Interior with a median supporting septum in each valve. 



Niagara dolomites. Near Milwaukee, Wisconsin. 



Parastrophia multiplicata, sp. nov. 



PLATE LXin, FIGS. 16, 18, 21. 



This species differs from P. Greenii in its more conspicuously developed me- 

 dian fold and sinus, flatter and larger plications, and the greater number of the 

 latter on the lateral slopes. The usually sessile spondylium of the brachial 

 valve may also prove a distinguishing feature. 



Niagara dolomites. Near Milwaukee, Wisconsin. 



