86 Clarence J. Elmore 



Fossil: Agate, Cherry County, Greeley County, Merriman, Mullen, 

 Thedford, Valentine. 



Belvidere, Blackpipe, Conata, Cutmeat, Interior, Kadoka, Little White 

 River, Norris, Rapid City, Rosebud, Scenic, Weta, S. Dak.; Devils Lake 

 and fresh water near Devils Lake, N. Dak. ; Cheyenne, Wyo. ; Stockton, 

 Cal. 



A form described as A^. cuspldata forma craticula is fouiid com- 

 monly with normal forms. In this condition there are about 4 

 heavy lines in lO/x besides the striations, connecting the thickened 

 margins with the heavy line along the raphe. These specimens are 

 identical in form with ordinary specimens of the species and the 

 arrangement of the endochrome is similar. I have never observed 

 them in motion. On January 13. 1896, I found a specimen in this 

 condition collected in a watering tank at Talmage, Nebraska, on 

 December 26, 1895. The endochrome was diffused through the 

 entire cell. After watching a few minutes the two valves sep- 

 arated, showing a new cell between them with ordinary valves. 

 After the forming of the new cell the old cell contained two 

 vacuoles and part of the endochrome which did not enter into the 

 new diatom. The new diatom was of practically the same size as 

 the old one. In the same collection another diatom had four oil 

 globules in each half of the cell, two large and two small, the 

 larger ones next to the center and the smaller ones at the ends. 

 In this collection there was one specimen of this form to about a 

 dozen in the normal condition. Fig. 382 shows a specimen with 

 8-9 very radiating striations in 10 /a in addition to the ordinary 

 striations. De Toni, vS'3'//. Alg., II, sec. i, p. 6, refers to this as 

 an " abnormal state." It has been called Stictiodesmis craticula 

 Grev. and SurircUa cratictda Ehr. 



8. SCULPTAE 



A. Apices rostrate or regular; longitudinal sulcus broad. 



52. A^. rostrata. 

 AA. Apices rostrate-capitate; longitudinal sulcus narrow. 



53. A^ sphacrophorn. 



52. Navicula rostrata Ehr. in Bcr., p. 18. 1840. 



Navicula sculpta Ehr. Mikro., pi. to, I. fig. 5. iSf;4. 

 PI. II, figs. 390-397; pl- 22, fig. 835. 



