1889.] NEW YORK ACADEMY OF SCIENCES. 35 



ginous rock occurs, in the liills immediately west of Lake Mer- 

 ced, they are found in a layer six feet thick. In looking over 

 the geological collection in the Bureau of Mining in San Fran- 

 cisco, I saw a rock-specimen from Lake Merced labelled "pum- 

 ice-stone." This specimen, in fact, gave tlie impetus for my trip 

 to the Lake Merced region and the coast hills. Arrived at the 

 spot, wliich is known as the pumice-stone mine, I discovered im- 

 mediately the nature of this deposit; it was simply a bed of 

 infusorial earth, conformable both above and below with sand- 

 stone layers; the dip is due west, sloping towards the Pacific. 



This protozootite, microscopically examined, presents the same 

 aspect as the ferruginous species, minus the organic detritus ; 

 the view of the mineral remains is therefore unobstructed and 

 very distinct. Diatoms are less frequent, but skeletons of 

 ciliata are abundant. 



A si)ecimen from Sonoma Co., forming a layer ten feet in 

 thickness, is very rich in diatoms, resembling the Virginia speci-r 

 mens closely: Melosira, Pleurosigma, and Navicula are the most 

 common forms. 



The Quaternary marl first mentioned contains also biological 

 detritus, especially the shells of a small brown rhizopod, and 

 likewise Navicula. Li the closed tube it behaves somewhat dif- 

 ferently from the ferruginous protozootite, showing that it con- 

 tains less organic detritus; only a trace of water is given; 

 hydrogen sulphide is developed; it blackens, but not as much 

 as the former, and contains some magnetic particles. This 

 Quaternary protozoan marl is composed of the following in- 

 gredients: — 



1. Disintegrated material of the protozootites and sand-rock 

 in the coast hills. 



2. Magnetic sand, abundant along the beach. 



3. Shells (entire and in fragments), — remains of living mol- 

 lusks. 



4. Shell fragments and detritus from Cretaceous rock-frag- 

 ments and pebbles washed on to the beach in large quantities. 



5. Biological detritus of the locality, such as rhizopods, etc. 



I have yet to report on another category of altered, impreg- 

 nated, or metamorphosed protozootites, — the bituminous and 

 asphaltic protozootite. In the list of California minerals we find 

 the mineral Jouite, under the heading of Lignite, as an obscure 

 hydrocarbon; it is generally found in contact with lignite or 

 asphaltum beds. Microscopical and chemical examination have 

 determined it as an asphaltic protozootite, in which the organic, 

 especially the vegetable, detritus is remarkable. Algai form the 

 principal part, — the cellular structure often well retained. Of 

 rhizopods, flagellata (Euglena) thecoflagellata (Phacus), etc.. 



