48 CALIFORNIA ACADEMY OF SCIENCES. [PROC. 30 SER. 



" No. 89. Pale gray or cream-tinted hard rock just 

 scratches with knife no action in acid. The section 

 examined showed numerous minute pores, but whether these 

 indicated spaces where organisms had been is doubtful. No 

 organisms could be recognized in this rock, which, never- 

 theless, appears to be of opalized silica. A few angular 

 chips could be distinguished in polarized light. 



" With the exception of this last specimen, the siliceous 

 and silico-calcareous rocks of the island of Santa Catalina 

 are remarkable for the very slight amount of alteration 

 which the structures of the siliceous and calcareous organ- 

 isms have undergone in the fossilization. Both the most 

 delicate diatoms and the Foraminifera occur in these beds 

 together, in nearly as well preserved condition as in deposits 

 now forming. The beds may well be compared with recent 

 diatomic oozes, and, as in these latter, there is a small per- 

 centage of sponge spicules, Radiolaria and Foraminifera 

 mingled with the prevailing diatoms. The paucity of Radi- 

 olaria in the beds is a peculiar feature. Sections of these 

 rocks show very distinctly that the entire material, down to 

 the smallest particles, is of organic remains mostly now 

 broken up, for the proportion of perfect forms is small 

 compared with the large quantity of fragmental debris. 

 The amount of the foreign angular mineral particles is insig- 

 nificant." 



Chemical Characters. This note would seem to leave no 

 room for question as to the organic origin of the shale, but 

 that the point might be considered from all sides, a chemical 

 determination was made of the amount of soluble silica in the 

 most earthy and least calcareous of the specimens. About a 

 a gram of the roughly powdered material was used, in a ten 

 per cent, solution of potassium hydrate. For the piirpose of 

 comparison specimens of pumice and nearly pure volcanic 

 ash were taken and subjected to the same treatment as the 

 shale. All the material was well dried at 100 (C) before 

 weighing and adding to the solution. The solutions were 

 brought to boiling twice, being allowed to stand some hours 

 in the interval, and for about a day after the second heating. 



