68 THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 



AMPHIPRORA EHR. (1843) 

 (amphi, on both ends, and prora, a prow) 



Frustule twisted in the longitudinal axis, constricted in the middle; zone complex, 

 with numerous divisions crossed by fine striae. Valve lanceolate, acute. The raphe con- 

 fined within a sigmoid keel or extension of the valve; the central and terminal nodules 

 indistinct. Strise transverse, punctate, with coarser striae at the junction of the keel and 

 lower part of the valve. 



Chromatophores single, with indented border except in A. pulchra, in which there 

 are two chromatophores with entire borders. 



AMPHIPRORA ALATA KUETZ. 



Frustule with a row of puncta at the junction line. Valve linear, acute at the ends. 

 Median line sigmoid. Strise lineate on the lower part of the valve, punctate on the keel. 

 Along the coast. Not common. 

 PI. 14, Fig. 3. 



AMPHIPRORA PULCHRA BAIL. 



Frustule with sigmoid connective zone. Valve very convex, with sinuate keel and 

 junction lines evident. In zone view and in valve view, one half of the frustule, owing to 

 the elevation of the keel, is wider than the other half. Stria? punctate, coarser on the keel. 



Not uncommon along the coast. 



PI. 14, Figs. 1 and 2. 



AMPHIPRORA CONSPICUA GREV. 



Valve linear or elliptical, with acute ends. Median line sigmoid, but the junction 

 lines not evident. Striae lineate, with coarser lines near the middle. 

 Not common. Port Penn, Delaware River. 

 PI. 14, Fig. 4. 



AMPHIPRORA ORNATA BAIL. 



Frustule membranaceous, constricted in the middle, with well-marked folds extending 

 from the junction line in both directions. Valve lanceolate, constricted in the middle and 

 with protracted ends. Keel undulate on the edge. 



A beautiful, transparent and delicate form, the only fresh-water species in our locality. 



Delaware Water Gap, Pa. 



PI. 14, Figs. 6 and 7. 



AMPHIPRORA PALUDOSA WM. SM. 



Frustule membranaceous, constricted, with truncate ends. Valve linear, with acute 

 ends. Striae scarcely visible. 

 Cape May (Cleve). 

 PI. 14, Fig. 5. 



TROPIDONEIS CLEVE (1891) 

 (tropis, a keel) 



Frustule oblong, constricted in the middle; keel not sigmoid. Axial area not evident. 

 Striae very fine, punctate, in longitudinal lines. 



