A1TENDIX. 
19 
PLACUNOHIA. Broderip. 
P. fragosa. Subrotund, compressed, surface of disk very irregular or 
uneven with small radiating irregular closely-arranged interrupted ribs, 
having a very rugose appearance ; cardinal process thick and broad, rib 
prominent. Length If inches. 
Locality. 20 miles north of Wilmington, Cape Fear River. 
RAETA. Gray. 
II. alta , pi. 3, fig. 3. Shell elevated, subtrigonal, inflated, rudely lineal 
concentrically ; umbo plicated, beaks nearer the posterior than the ante- 
rior end ; posterior end regular. 
R. erecta. Shell subtriangular, thin in substance, inflated anteriorly, 
umbo not oblique, sculptured with prominent subacute slightly waved 
concentric folds or ribs, which on the rest of the valve are less prominent, 
where it is sculptured with fine hieroglyphic wrinkles ; anterior end ob- 
tuse ; cartilage pit large ; length 2f inches ; height 2 inches. 
Locality. Goldsboro’, FT. C. 
The species diliers from R. canaliculata in being proportionally higher, 
and without obliquity of umbo, while the ribs on the loweir half of the 
valve are less prominent and regular. The cartilage pit is proportionally 
much larger than that of the allied species. 
A BRA. Leach. 
A. beUa , pi. 3, fig. 4, 6. Triangular, solid, and sculptured with close, 
very numerous fine reticulated striae, the concentric lines sharp and more 
prominent than the radii, which are flattened ; fold distinct ; beak situated 
behind the middle of the valve ; cardinal and lateral teeth prominent. 
Locality. Wilmington, IN’. C. Prof. Kerr. 
A. Ilolmesii , pi. 3, fig. 8. Shell oval, convex with numerous concentric 
lines, beaks nearest the posterior end ; margin rounded ; posterior end 
obtusely rounded. 
Syndosmya carinata , Tuomey and Holmes (not Conrad) Plio. Foss. S. 
C. pi. 25, fig. 2. 
NOETXA. Gray. 
W. protexta, pi. 3, fig. 5. Rhomboidal, ventricose about the umbonal 
slope, which is angular; disks widely contracted or impressed from beak 
to base ; ribs 31 or 32, bifid on the post-umbonal slope, which is impressed 
