40 SANTA MARIA OIL DISTRICT, CALIFORNIA. 
this shale is made of diatom skeletons. * * * Even when the 
rocks are flinty they often contain good impressions of Foraminifera.” 
Foraminifera occur in the partially calcareous shales of the Santa 
Maria district, and in places the limestone is full of them. In some 
specimens they are perfectly preserved and various kinds may be 
easily seen with the unaided eye. In other places the limestone 
shows no trace of organisms; but it is the opinion of the writers that 
they have been present in such places and have lost their shape, and 
that foraminiferal skeletons account for a large part of all the Mon¬ 
terey limestone and for the calcareous portion of the limy shales. 
H. W. Fairbanks says in his paper quoted on page — that the lime¬ 
stone of the Point Sal region “ appears to be formed almost exclu¬ 
sively of minute organisms/’ 
Specimens representing different varieties of the Monterey shale 
and flint were sent to F. J. Keeley, of the Philadelphia Academy of 
Natural Sciences, who very kindly made examinations of them and 
reported regarding their diatom contents. (See Pis. XIX and XX.) 
He found diatoms plentiful in the unaltered earthy shale and less com¬ 
mon in the more compact shale and in the less pure, either gritty or 
argillaceous shale. Sponge spicules were common in all the samples, 
and in those last mentioned they were more abundant than diatoms. 
No examination was made of the indurated varieties. Mr. Keeley 
was unable to make more than a hasty examination, but on request 
he estimated roughly that the purest material contained from 5 to 10 
per cent of diatoms and that the soft shale in which fewer could be 
seen contained possibly 1 per cent. He found a few Radiolaria but 
no Foraminifera in the pure siliceous shale, diatoms and next to them 
sponge spicules being by far the predominant organic remains. 
C. S. Boyer, of the Philadelphia Academy of Natural Sciences, kindly 
identified the species of diatoms in two slides prepared by Mr. Keeley 
from the two purest samples of diatomaceous earth that were sent to 
him. Mr. Keeley says: “The lists made by Mr. Boyer cover only 
the species he saw in the slides sent him, and an exhaustive examina¬ 
tion of the material, which would require searching over, say, a hun¬ 
dred slides or more, would probably give a long list of species, many 
of which might not be seen more than once or twice in the course of 
such an examination.” Nevertheless, these lists probably indicate 
the commonest species. In the slide made from the shale at the base 
of the Monterey from the locality above referred to at the junction 
of Salsipuedes and El Jaro creeks Mr. Boyer found the following 
diatoms: 
Coscinodiscus marginatus Ehrenberg. 
Coscinodiscus marginatus var. intermedia Rattray. 
Coscinodiscus robustus Grev. 
Arachnodiscus (fragment). 
Diploneis? (fragment). 
Melosira sulcata Ehrenberg (rare). 
