46 THE DIATOMACE^: OF PHILADELPHIA AND VICINITY 



RHAPHONEIS EHR. (1844) 

 (rhaphis, a needle) 



Frustule in zone view linear. Valve lanceolate or elliptical-lanceolate; pseudoraphe 

 distinct; striae radiating, moniliform. 



RHAPHONEIS AMPHICEROS EHR. 



Valve lanceolate, broad, with apices produced; striae in curved lines, moniliform, the 

 large granules in longitudinal lines. 

 Blue clay. 

 PL 10, Fig. 38. 



RHAPHONEIS AMPHICEROS VAR. RHOMBICA GRUN. 



Valve as in type form but shorter, with larger and more remote granules. 



Blue clay. 



PL 10, Figs. 39 and 40. 



RHAPHONEIS BELGICA VAR. INTERMEDIA GRUN. 



Valve lanceolate, rostrate; granules in longitudinal and nearly transverse, not 

 radiating, lines. 

 Absecon, N. J. 

 PL 10, Fig. 41. 



DlMEROGRAMMA RALFS (1861) 



(dis, two, meros, a part, gramma, a letter) 



Frustules quadrangular, inflated at the angles, in fasciae. Valve ovate or lanceolate; 

 striae moniliform, transverse or slightly radiate; median area or pseudoraphe broad, 

 lanceolate. 



DlMEROGRAMMA MARINUM (GREG.) RALFS 



Valve lanceolate or linear and inflated in the middle; striae moniliform, transverse or 

 slightly radiate; median area linear or lanceolate, sometimes not reaching the smooth ex- 

 tremities; striae, 8 in 10 /i. 



PL 12, Figs. 9 and 10. 



Fig. 9 differs in its lanceolate outline, in having four puncta on each side in a row, and 

 in the striae which are radiate. 



DlMEROGRAMMA SURIRELLA (EHR.) GRUN. 



Valve elliptical-lanceolate, with rounded apices; striae moniliform, radiate; pseudo- 

 raphe narrow, lanceolate. 

 Blue clay. 

 PL 12, Fig. 11. 



