1899] MICROSCOPICAL JOURNAL. 55 



niagarae. Van Heurck (Synop. des Diat. de Belg. 1880, 

 plate X C V, fig. 1-14) published it as S. carconinensis, 

 Grun.; S. astrea (Ehr.) Grun. (Discoplea astrea, Ehr. 

 Cyclotella rotula, Kutz.); St. astrea var spinulosa, Grun. 

 (S. agyptiacus, Ehr.); St. astrea var minutula, Grun. (Cy- 

 clotella minutula, Kutz.; Discoplea oregonica, Ehr.); St. 

 hautzschianus, Grun.; (Cyclotella operculata, Hantsch. 

 Rab. Alg. Europ. 1104, St. balticus, Schur.); Idem var 

 pusilla, Grun. S. C. (bellus A. Schmidt var?); Novse 

 Zealandise, Cleve; St. niagarse, Ehr. (Cyclotella spinosa, 

 Schumann). 



The foregoing are all Cyclotella with or without spines. 

 They are C. berolinensis, C. G. E. They include Disco- 

 plea astrea, C. G. E. Or, they are Discoplea greca, C. G. 

 E. 1840, Ber. p. 208. I think they are sporangia (i. e. 

 large forms) of Melosira granulata, C. G. E. Abhan- 

 deungen (Amer.) p. 187. M. granulata is very common 

 in the deposits of the Occidental Sea. I have at least a 

 dozen or two from the North and the South, from Wash- 

 ington and from Texas, from Kansas to California. 



There is also present, and nearly as common as the Cy- 

 clotella, another form which it would be difficult to ex- 

 plain in a strictly fresh-water deposit. It is Hyalodiscus 

 scoticus, F. T. K. and is decidedly marine. It is found 

 everywhere on the sea coast growing in salt-water. It 

 was first found on the coast of Scotland and named Cy- 

 clotella scotica by Kutzing in 1844 (Die kieselschaligen 

 Bacillarien oder Diatomeen). It includes Podosira and is 

 included in Melosira. How it was evolved is difficult to 

 understand but as Melosira is extremely common and va- 

 ries in form almost indefinitely it may have come from one 

 of its common forms. 



In Van Henrck's Synopsis, pi. 134 are 24 figures in- 

 cluded in Hyalodiscus — Podosira, seven genera and sev- 

 eral so-called species, and yet they are all one form. 



