36 THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 



According to T. H. Buffham (Jour. Quek. M. C., Series 2, Vol. 2, p. 131), the frus- 

 tules are of two kinds, those in which the length and breadth are the same and those which 

 are much lengthened, with a wide hyaline girdle frequently in the middle. At the time of 

 fructification the smaller frustules are attached to a larger one which produces a sporan- 

 gium at the end of the girdle from which the other end of the frustule has disappeared, or, 

 if the two halves of the frustule remain, two sporangia are formed. 



RHABDONEMA MINUTUM KUETZ. 



Frustules small; valve not smooth at the ends, elliptical or lanceolate-elliptical, with 

 transverse rows of puncta; pseudoraphe distinct. Foramen single, alternating above and 

 below in adjoining partitions. 



Common in the blue clay and along the coast. 



PI. 8, Fig. 7 and PI. 38, Fig. 11. 



RHABDONEMA ADRIATICUM KUETZ. 



Valve linear-lanceolate, with smooth angles; rows of puncta transverse, the intervals 

 appearing as costse, as in arcuatum. Foramina, three. 



Blue clay in the Pensauken and Pavonia deposits and along the coast. 

 PI. 8, Figs. 4, 5 and 6. 



TABELLARIA EHR. (1839) 

 (tabella, a tablet) 



Frustules quadrangular, adnate in filaments, frequently found in zig-zag chains, united 

 by a gelatinous isthmus, at length separating. Valve linear, inflated in the middle and at 

 the ends ; striae transverse. 



Chromatophores numerous, small, along the zones. 



TABELLARIA FENESTRATA (LYNG.) KUETZ. 



Valve elongated; pseudoraphe narrow; transverse striae faint. In the zone view a 

 straight septum is shown at each end of a valve. 



Common, especially in the cedar swamps and ponds of the Pine Barren region, N. J. 

 PI. 8, Figs. 11 and 12. 



TABELLARIA FLOCCULOSA (ROTH) KUETZ. 



Valve linear, with median inflation larger than the terminal; pseudoraphe rather broad 

 in the middle; transverse striae subtly punctate. In zone view the frustules are quadrangu- 

 lar, or nearly so, with about six sometimes curved septa at one end alternating with those 

 on the other end. 



Conferva flocculosa Roth. 



Common especially in the Pine Barrens of New Jersey. 



PL 8, Figs. 8, 9 and 10. 



GRAMMATOPHORA EHR. (1840) 

 (from gramma, a letter, and phoreo, I bear) 



Frustules quadrangular, adnate, in zig-zag, united by an isthmus, or, usually, found 

 free; divided by two sinuate and perforate curved septa. Valve linear or oblong, sometimes 

 with sinuate sides, and with a pseudoraphe and transverse punctate lines. 



Chromatophores granular. 



