A. M. KDWAKDS ON A (>lArOMA<;KODS KARTH. '203 



Cocconeis Mexicana, Ehr. Navicula cuspidata, Ktz. 



Cymatopleura elUpHca, var. „ duhia, W. G. 



Bihernica, W. S. „ pygmcea, Ehr. 



Cymatopleura solea, A. de B. „ sculpta, Ehr. 



Cymhella cistula, Hempr. „ viridis, Ehr. 



Epiihemia gihha, Ehr. Bhoicosplienia curvata, Ktz. 



„ turgida, Ktz. Surirella hiseriata, A. de B. 



Fragillar'ia virescens, Ralfs. „ spiralis, Ktz. 



Gomphonema gracile, Ehr. Synedra ulna, Ehr. 



Melosira granulata, Ehr. 

 The Cocconeis lineata, Ehr., is a large form of Cocconeis placen- 

 tula, Ehr., as is seen plainly in this sample. But the Cocconeis 

 placentula, Ehr., in it has the markings coarse, showing the 

 transition into a salt water form, or Cocconeis scutellum, Ehr. 

 The Navicula diihia , W. G., is plainly a form of Neidiiim, E. P. 

 (E. Pfitzer. Untersuch. ii. Ban und Entvvick. d. Bacillariaceen 

 (Diatomaceen) 1871), or Navicula firma, Ktz. Uhoicosphenia 

 curvata, Ktz., has a var. viarinum, W. S., which is marine, but 

 this is'not the point on which I wish to dwell. What I wish 

 to indicate is the occurrence of Biddnlpliia Icevis, Ehr ., a form 

 hitherto ranked as marine in this, a fresh water deposit. Now 

 this form is very common in the United States. As marine it oc- 

 curs on the coast from Cape Cod round into the Gulf of Mexico. 

 As brackish it is found in the salt marshes of Nebraska and other 

 western localities. As a fresh water form it occurs in a pool 

 near Newark, N. J., and in a spring near Coney Island, N.Y. 



Fossil it is found in the fresh water deposit of Guatemala, 

 and at Hatfield Swamp, N.J., which I will describe below. 

 And as a brackish fossil form it is found in a deposit called, 

 for want of a better designation, Champlain, near Newark, 

 N. J., and which I propose to describe in a further paper. 



Coccon eis Mexicana, E hr., is a very small form, looking like 

 Navicula exilis, Ktz., only smaller, with superior valve having 

 median canal, and fastened by the valve to an alga or stone, as 

 is the case with those in the Guatemala Diatomite. In this 

 latter, besides the Diatomacese, there is only found fragments 

 of what I have already judged to be pumice. These are com- 

 mon in the Diatomaceous deposits- on the Pacific slope, and 

 upon this pumice is the Cocconeis Mexicana. This shows that 

 a volcano existed near by where the Diatomite was formed. C. 



