MAEYLAND GEOLOGICAL SURVEY 487 



CRYPTOGAMIA. 

 THALLOPHYTA. 



Class ALGi^. 



Order DIATOMACE/E/ 



Tribe RAPHIDIE/E. 

 Family CYMBELLE>E. 



Genus CYMBELLA, C. Azardk. 

 Cymbella cistula (Hemprick). 



Family NAVICULE/E. 



Genus NAVICULA Bory. 



Navicula praetexta Ehrenberg. 



Navicula schaarschmidtii Pantocsek. 



Navicula schultzei Kain. 



N'avicula Kennedyi Wm. Smith. 



Navicula LYRA Ehrenberg. 



Genus DIPLONEIS Ehrenberg. 



Diploneis microtatos var, christianii Cleve. 

 Plate CXXXV, Fig. 5. 



Shapidodiscus marylandica Christian, 1887, The Microscope, vol. vii, p. 67. 

 Rhapidodiscus Christianii Gascoyne, 1887, The Microscope, vol. vii, p. 67. 

 Rhapidodiscus Pebigerii Christian, 1887, The Microscope, vol. vii, pp. 66, 67. tigs. 

 Diploneis microtatos var. Chi-istianii Cleve, 189i, Naviculoid Forms, pt. i, p. 96, pi. 

 ii, fig. 1. 



Description.- — Valve orbicular. Diam. .039 mm. Eows of alveoli radiat- 

 ing from the median line, indistinct in the middle. " Median line with 

 distant central pores, and ending at a considerable distance from the 



1 The most common and important diatoms are alone figured and described. The 

 iindescribed forms have been determined by. the author from several collections 

 placed at his disposal. 



