MOLLUSCA. 501 



1886. Paranomia lineata Whitf., Pal. N. J., vol. i (Monog. 



U. S. G. S., vol. 9), p. 45, pi. 9, fig. 10. 

 1905. Paranomia scabra Johns., Proc. Acad. Nat. Sci. Phil. 



(1905), p. 12. 

 1905. Paranomia lineata Johns., Proc. Acad. Nat. Sci. Phil. 



(1905), p. 12. 

 1905. Paranomia saffordi Johns., Proc. Acad. Nat. Sci. Phil., 



1905, p. 12. 



Description. Shell thin and fragile, broadly and irregularly 

 subovate in outline, the dimensions of the largest individual 

 observed being: length from beak to opposite border, 55 mm.; 

 width at right angles to the last dimension, 54 mm. The dimen- 

 sions of an individual of more nearly average size are: length, 

 31 mm.; width, 34 mm. The upper valve depressed convex, 

 the surface marked by distant, rounded, elevated radiating ribs, 

 which are frequently more or less wavy in their direction and 

 become stronger towards the front of the shell. At irregular 

 intervals the ribs are produced into hollow spines directed away 

 from the beak, which become larger and more distant as the ribs 

 increase in strength towards the front of the shell; the spaces 

 between the ribs are broad and flat, being three or four times 

 as wide as the ribs, and on the best preserved shells are marked 

 with rather delicate concentric lines. The lower valve is convex 

 towards the beak, where it is apparently broadly perforate, 

 becoming concave towards the front of the valve. The surface 

 markings are similar to those of the upper valve, though in some 

 cases the ribs and spines seem to be less strongly developed. 



Remarks.* This species occurs most commonly in the Mar- 

 shalltown clay-marl, from which formation near Swedesboro 

 a large number of individuals retaining the shell have been col- 

 lected. None of them are so large as the specimen illustrated 

 by Whitfield under the name of P. lineata, but they all exhibit 

 the same essential specific characters as that shell. Whitfield 

 was in error, however, in considering the specimen he used for 

 study as a perforate valve, the apparent perforation near the 

 beak being only a fracture. In none of the Swedesboro speci- 



