88 THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 



Considered by Cleve as synonymous with M. apiculata Grun., not Wm. Smith, and 

 by De Toni as synonymous with M. apiculata Wm. Sm. In any case, M. angulata Lewis 

 is not the same as M. apiculata Wm. Sm., the loculi of which are equal. 

 Atlantic City. H. L. Smith T. S. No. 211. 

 PI. 17, Fig. 17. 



STAURONEIS EHR. (1843) 

 (stauros, a cross, and neis (naus), a boat) 



Frustules free, sometimes geminate; valve as in Navicula but with a stauros. Cell 

 contents as in Navicula. Mereschkowsky, however, says that the chromatophores always 

 contain more pyrenoids than are found in Navicula. Heinzerling gives the number as two 

 to four in each chromatophore. 



Cleve includes under Naviculse Microstigmaticse all species of Stauroneis, Pleuro- 

 stauron, Schizostauron, certain Schizonemse and Naviculse. As a matter of convenience, 

 and because I have already included certain Schizonemse and Scoliopleura under Navicula, 

 and because of the small number of species in our locality, I have arranged them under 

 the three divisions of Cleve as follows : 



Stauroneis. Forms having a true stauros, without diaphragms. 



Pleurostauron. Forms like Stauroneis but with diaphragms at the ends. 



Schizostauron. Forms having a bifid stauros. 



STAURONEIS PHCENICENTERON EHR. 



Valve lanceolate, obtuse; strise radiate, 18 in 10 n, distinctly punctate. L. usually 

 125 M but sometimes 200 M- 

 Common in fresh water. 

 PI. 27, Fig. 1. 



STAURONEIS ANCEPS EHR. 



Valve lanceolate, with rostrate or capitate ends; stauros in some cases does not reach 

 the margin. The varieties are very numerous. 



Var. gracilis (Ehr.) Cl. Valve lanceolate, strise very fine; margin of stauros striated. 

 L. 100 M. Cape May, N. J. PI. 27, Fig. 5. 



Var. amphicephala (Kuetz.) Cl. Valve capitate at the ends; strise, 24 in 10 ju. L. 47 ft. 

 Fresh water. PI. 27, Fig. 7. 



Var. ? Valve with produced ends; strise, 30 or more in 10 // L- 104 ju. Willistown, 

 Pa. PL 27, Fig. 4. 



Var. ? Valve with produced ends; strise, about 28 in 10 p., punctate. L. 47 n. New- 

 town Square. PI. 27, Fig. 8. 



Var. ? Valve with produced ends; strise, 22 in 10 n, showing a tendency to form 

 longitudinal rows of puncta as in Stauroneis stodderi Greenleaf, but the rows are not so 

 evident. L. 60 p.. Pavonia, N. J., artesian well. PL 27, Fig. 9. 



STAURONEIS FRICKEI VAR. ANGUSTA N. VAR. 



Valve lanceolate, gradually tapering to the obtuse ends; terminal fissures prominent, 

 forking at a distance of 7 p, from the ends. Frustules frequently geminate. L. 173 ju. 



Newtown Square. Rare. 



PL 26, Fig. 18. 



Near Stauroneis frickei A. S. (Atlas, PL 242, Fig. 16), except that the stauros is narrow 

 at the margin. 



