the specimen (and naming was put before studying). They saw from 

 prepared or rather from scattered specimens and not from living 

 forms. As I have already pointed out it is easy to name a thing but 

 it is more difjkult to study it. Hence the confusion of « species » 

 and « genera ». Bailey thought evidently that locality was « specific ». 

 Hence he called a form which grew in the Atlantic Hyalodiscus sub- 

 tilis, and on the Pacific Hyalodiscus californicus although they were 

 the same. Ehrenberg had found at the far north a form which he 

 called Hyalodiscus Frankliniì, in the fossil state at Richmond, Virgi- 

 nia, Hyalodiscus laevis, in the fossil state at Patagonia Hyalodiscus 

 Palagonicus and in the interior of North America Hyalodiscus Whit- 

 neyì. These are ali exactly the same. Hence the confusion of « spe- 

 cies » and 1 may say « genera » also. In January 1877 I went to 

 California among other things to study the Bacillaria living and the 

 celebrated sfrata of Monterey and elsewhere. Then I had the Hya- 

 lodiscus (of course called by Bailey Hyalodiscus Califomicus) gro- 

 wing in profusion in San Francisco harbour. There I collected it 

 and a thorough chance to study it. I had it ali along the coast of 

 the Pacific. I also colleced it at Sacelito just opposite to San Fran- 

 cisco, on the north side of the Golden Gate, a form which proved to 

 be Hyalodiscus cervinus T. B. Brightwell had seen it from a prepa- 

 red acid cleaned specimen. But I had it living. It was attached by 

 the edge to an alga. I thought it was different from Hyalodiscus sub- 

 tilis for the markings were coarse, being resolvable with a 2-3dr of 

 an inch and with centrai light. The centre of the disc is not mar- 

 ked like Hyalodiscus subtilis being not cut off from the surrounding 

 portion, but the dots are over the whole valve and show plainly. 

 They also look plainly hexagonal in form. Hyalodiscus subtilis was 

 founded by Bailey in his Notes on new species and localities of 

 microscopie organisms, Washington i852, page io, fìgur 12. This 

 figur is a good one for the time it was engraved on steel by J. E. 

 Gavit. Sometimes there are indications of an umbilicus as it is cal- 

 led but otherwise with the exceptions of the markings in Hyalodi- 

 scus subtilis being fine and in Hyalodiscus cervinus being coarse 

 they are alike. 



A Hyalodiscus like form is found at Abishiri in Japan, fossil, 

 which has the umbilicus with scattered spines and is larger than 



