The Microscope. 329 



down the valley the same sort of preponderance was shown by Cos 

 craspedodiscus. 



In March, 1876, a fragment of diatom earth was found rolling 

 in the tidal refuse some miles south-east of Santa Monica, Cal., by 

 Mr. T. P. Woodward. There was no sign of any diatom deposit in 

 the vicinity. On examination this was found to be exceptionally 

 rich in all the finest diatoms of the Pacific Coast. Subsequent 

 researches have failed to bring to light another specimen of equal 

 richness and beauty, although several have been found which 

 approximate it. It seems probable, therefore, that the same varia- 

 tions occur in both of these great marine deposits, and that a dupli- 

 cation of exceptionally rich specimens is hardly to be expected. For 

 two months past the Richmond and Chesapeake Railroad Company 

 have been cutting a tunnel on Eighth Street, which will run directly 

 through the diatomaceous stratum. After a great many examina- 

 tions of the earth brought to view, several specimens have been 

 found bearmg nearly the same relation to the ordinaiy deposit as 

 the Santa Monica find does to other California deposits of fossil 

 diatoms. In one or two of these the small forms (mostly Synedra) 

 are concentrated in minute pockets, from which, if carefully 

 removed, they may be mounted pure and clean without any treat- 

 ment. A series of five slides prepared from this earth shows abun- 

 dantly the following beautiful forms, which are exceedingly rare 

 elsewhere at Richmond, viz : Aulacodiscus crux, Asteromphalii, 

 large and fine, equal to St. Monica, Eupodiscus argus, Trie tridacty- 

 lum and T. Marylandica. There are also occasional specimens of 

 Coscinodiscus sol, Climacosphenia moniligera. Trie Balearix, five- 

 pointed, similar to the South American variety, Eupodiscus, supposed 

 to be a new species, and a beautiful variety of A. Crux with five pro- 

 cesses, one form, closely resembling the ancient grain mills dug out 

 at Pompeii, I cannot classify. A minute fragment of the earth taken 

 from a dump gives a most extraordinary showing of the large forms, 

 especially Cos gigas, one of the finest of the Richmond diatoms. 



These interesting results having been obtained by the examina- 

 tion of two or three dozen slides, it would seem reasonable to hope 

 that the further study of this new material will considerably enlarge 

 the catalogue of Richmond diatoms. Diatoms thrive best in clear, 

 still waters, and the cold of Arctic and Antartic seas seems favorable 

 to their growth. It is evident from examination of the Virginia 

 deposits that currents contaminated with sand and mud eventually 

 destroy them. It would therefore seem fair to argue that an Arctic 



