18 THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 



HYALODISCUS SCOTICUS (KUETZ.) GRUN. 



Valve small, with puncta about 24 in 10 /x, appearing hyaline. 



De Toni remarks that it resembles a small form of H. subtilis which occurs north and 

 south of our limits and is yet likely to be recorded. 



Cyclotella scotica Kuetz. 



Podosira hormoides Wm. Sm. 



Blue clay. Not rare. 



PL 1, Fig. 20. 



Endochrome in the form of four flaps or patches bound together about a common 

 pyrenoid. In H. subtilis numerous rod-shaped chromatophores lie in a row and are not 

 bound in the centre (Mereschkowsky). 



STEPHANOPYXIS EHK. (1844) em. GRUN. (1884) 

 (stephanos, a crown, and pyxis, a kind of vase or box) 



Frustules ellipsoidal, concatenate; valves tumid, of unequal convexity, coarsely areo- 

 late, the cells in rows parallel to the longitudinal axis, not radiate, with stray spines or 

 teeth placed concentrically more or less near the margin. 



According to Karsten the chromatophores are round or angular discs which lie near 

 the connective zone. 



STEPHANOPYXIS TURRIS (GREV.) RALFS 



Valve cylindrical, with a crown of stout spines less than the diameter of the valve 

 near the margin. Cells hexagonal, about 2 in 10 M, sometimes punctate. The valve hav- 

 ing the greater convexity has the larger spines, though usually less of them. 



Creswellia turris Grev. (Gregory, Diat. of the Clyde, T. R. S. E., vol. 21, part 4, p. 66.) 



Stephanopyxis appendiculata Ehr.? 



Creswellia is incorrectly based, as stated by Ralfs, on the concatenation of the valves 

 which was not noticed by Ehrenberg in the fossil forms. It had been suggested by Kuetz- 

 ing in Systema Algarum (p. 126). 



Blue clay. Port Penn and Smith's Island. 



PL 2, Figs. 1 and 2. 



STEPHANOPYXIS CORONA (EHR.) GRUN. 



Valve larger than in turris, sub-globose, coarsely areolate cells, 4-5 in 10 M. One valve 

 furnished with a crown of teeth shaped like the letter T and united at the top into a ring 

 above the margin of the valve; the other valve with long spines more or less concentrically 

 arranged. 



Blue clay. Not common. Fossil in the Nottingham deposit. 



PL 2, Fig. 3. 



NOTE. The diatomaceous deposit, so often called "Bermuda" or "Bermuda tripoli, " 

 especially by foreign writers, is in reality the Miocene stratum extending for miles along 

 the Patuxent River near the village of Nottingham, Md. The author is perfectly familiar 

 with the location, having made large collections there. The mistake in the name is due to 

 the fact that Prof. Bailey received material from Mr. Tuomey marked "Bermuda Hun- 

 dred," which is located near Petersburg, Va. Attempts have been made to find material 

 there and while there is an earth containing Miocene diatoms at Petersburg, it does not 

 exactly correspond to the material sent to Ehrenberg by Bailey, who was in doubt as 

 to the locality. The Bermuda Islands are of coral formation and have no deposits of 

 diatomaceous earth. 



