Rathbun.] 32 [May 15, 



A few specimens of Retzia, which probably represent only a variety 

 of R. Wardkina^ are contained in the collections made on the Rios 

 Majcuru and Curiui. They agree in form with the Erere spo(;imens, 

 but the ])lications on the shells from the two former localities are 

 slijibtly larger, and fewer in number, there being about twelve on 

 each valve. 



Devonian sandstone, Erere. (Morgan Exs., 1870 and '71 ; Geol 

 Comm., '76.) Rios Mtecurii and Curua. (Geol. Coram., 1876.) 

 Rhynchonella ererensis, sp. nov. 



Shell of large size, suborbicular in shape and marked with promi- 

 nent, separated plications; length only very slightly greater than the 

 width; thickness through the two valves apparently nearly equal to 

 the width. 



Dorsal valve subcircular in outline with a slightly projecting, 

 sharply pointed beak ; cardinal margins moderately concave and ex- 

 tending far forward. Viewed from the side, the surfiice rises rapidly 

 upward from the beak, along the median line, in quite a regular 

 curve for about one-half the length, whence to near the front the sur- 

 face is quite straight, but slightly rising. It curves abruptly down- 

 wards toward the ventral valve, and is much flattened on each side 

 of the front margins of both valves. From side to side the curvature 

 of the dorsal valve is very strong, but not regular, the valve being 

 somewhat flattened along the median line, especially toward the um- 

 bone. 



The median fold begins near the centre of the valve, and increases 

 only slightly in prominence towards the front. Its width is about 

 two-fifths that of the valve, and it is marked with four prominent) 

 rounded or sub-angular plications, which are separated by similar de- 

 pressions. On each side of the fold there are six well defined plica- 

 tions, and besides these exist one or two very indistinct ones near 

 ■ the hinge. The plications nearest the fold are the most prominent, 

 being slightly smaller than those of the fold; they are rounded on top 

 or slightly angular, and each slopes down more gradually on its outer 

 than on its inner side. The depressions sepsirating the plications are 

 from two to three times the width of the latter. The plications are 

 only faintly indicated on the umbonal region; they cause the anterior 

 margins of both valves to be strongly digitate. The median septum 

 of the ventral valve reaches about half way to the front; it is promi- 

 nent and heavy near the beak, but grows gradually more slender for- 

 ward, being reduced to a mere line near the centre of the valve. 



