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



Clemente Island, some twenty-five miles further south. 

 If, then, these deposits are a part of the extensive Miocene 

 shales, we cannot consider their development as in any way 

 local, or as influenced by the deposits with which they are 

 associated, for the conditions favorable for the development 

 of the micro-organisms of the shale at that time must have 

 been far reaching. Except for the few microscopic frag- 

 ments, the shale as it occurs here is in general peculiarly 

 free from the tufaceous material with which it is associated, 

 indicating a considerable interval of quiet deposit, inter- 

 rupted at times by violent local volcanic outbursts. Santa 

 Catalina at this time was an island, as now, though doubtless 

 separated from the mainland by a considerably greater 

 expanse of water. The true relative attitude of island and 

 mainland and the intermediate channel can be revealed 

 only from the neighboring coastal formations. In addition 

 to other evidence, the porous character of some of the 

 lavas associated with the tuff and diatomaceous earth, and 

 the remains of large pectens found in the tuff, indicate that 

 these deposits could not have been formed in abyssal depths. 

 It would appear from other reasons that they were laid down 

 in not more than 600 or 1,000 feet of water. 



Analysis of Limestone. For the purpose of ascertaining 

 the character of the limestone, a partial analysis was made 

 by dissolving fragments in acid, and determining the amount 

 of the constituents in the solution thus obtained. The 

 results were as follows : 



Insoluble residue 8.234 



Fe 2 2 3 3 (alittle)} 2 ' 862 



CaO 27.944 



MgO 13.012 



Ignitionandj 43 6l5 



No determination of the alkalies was made. A qualita- 

 tive examination was made for phosphoric acid, but no 

 quantitative determination, though considerable was found 

 to be present. The residue in this case also was examined 



