MARYLAND GEOLOGICAL SURVEY 605 



those of Placenta, but obviously of different function. The genus is a 

 puzzle and cannot as yet be safely united with any other." Dall, 1 1898. 



A. Outline circular; radials relatively fine and crowded. . . .Paranomia scabra 



B. Outline ovate; radials relatively coarse and distant Paranomia lineata 



PARAXOMIA SCABRA (Morton) Conrad 



Placuna scabra Morton, 1834, Syn. Org. Rem. Cret. Group U. S., p. 62. 

 Placunomia scabra Meek, 1864, Check List Inv. Fossils, N. A., Cret. and 



Jur., p. 6. 



Paranomia scabra Conrad, 1867, Am. Jour. Conch., vol. iii, p. 8. 

 Paranomia scabra Conrad, 1868, Cook's Geol. of New Jersey, p. 724. 

 Paranomia scabra Whitfield, 1885, Mon. U. S. Geol. Survey, vol. ix, p. 44, 



pi. x, fig. 10. 



Paranomia scabra Johnson, 1905, Proc. Acad. Nat. Sci., Phila., p. 12. 

 Paranomia scabra Weller, 1907, Geol. Survey of New Jersey, Pal., vol. iv, 



p. 500, pi. Iii, figs. 10-13 (ex parte). 



Description. " With numerous beaded costse, radiating from the hinge 

 to the margin; shell thin, suborbicular, compressed. From one inch to 

 three inches in diameter." Morton, 183-1. 



Type Locality. New Jersey. 



The type specimen figured by Whitfield in 1885 is a mere frag- 

 ment which, as that eminent New Jersey paleontologist has observed, is 

 " scarcely sufficient for generic identification." However, its reference 

 to Paranomia is probably justified. The species as delimited by the aid of 

 later collections is thin, flattened and subcircular in outline, sculptured 

 externally with approximately thirty rather fine radials which occasionally 

 diastomose and which are quite sharply spinose toward the ventral margin. 

 The intercostal areas are narrow, scarcely or not at all exceeding the 

 costals in width. The incremental sculpture is quite vigorous and suffi- 

 cient to imbricate the radial. 



Paranomia saffordi Conrad from Tennessee and the type of the genus 

 develop apparently a much more regular and rather coarser and more dis- 

 tant radial sculpture. Paranomia lineata Conrad runs smaller, is ovate 

 rather than subcircular and has fewer, more prominent and more widely 

 spaced radials. Although it is not impossible that a connecting series may 



1 Trans. Wagner Free Inst. Sci., Phila,, vol. iii, pt. iv, p. 773. 



