NEOCENE STRATIGRAPHY. 34I 



that basis assigns the middle layer on San Pedro Hill to 

 the Pliocene.* 



It is hoped that the few hours spent there while work- 

 ing up this paper will put the geology at that point in a 

 little clearer light and on a more substantial basis, and it 

 is thought that Dr. Ball's conclusions will be substantiated. 



Surrounding the hill on the east and north is a very 

 broad terrace, from 20 to 40 feet above tide, most of the 

 town of San Pedro being on this terrace. Near the depot 

 this terrace is still flanked by soft deposits. At the top is 

 a layer, two feet thick, of black sandy soil, containing 

 vcidiny Pecten cBquisidcatiis Cpr., Chione simiUima Sby., 

 and other living shells. This bed will be treated more 

 fully under the Quaternary. Below that bed are three 

 to four feet of dark sand, then another thin layer, which 

 is quite fossiliferous, and is the middle layer referred to 

 above. Below that is a sandy deposit that has all the 

 appearance of sanddune structure. At the entrance to 

 the harbor this lower deposit is cut away and a recent sea- 

 cliff runs out to Point Fermin and around the island. 

 The middle layer or Pliocene is exposed at the top of this 

 cliff lying uncomformably on the disturbed Miocene. At 

 one point, where a short drain has cut into the cliff, the 

 Pliocene layer is especially fossiliferous. 



Altogether 125—150 species were collected in this layer, 

 of which number 104 species have been determined spe- 

 cifically. 



In the following list of Pliocene fossils collected at San 

 Pedro the first column gives those which have been re- 

 ported! from the Miocene; the second gives those pre- 

 viously reported from the Pliocene, most of which are 



''Univ. of Cal., Bull. Dept. GeoL, vol. i, p. 128. 



t From Dr. Cooper's list, 7th Ann. Eep. State Mineralogist, 1888, pp. 

 223 et seq. 



