AKNULU — THE rALKONTULUtiV AND Sl'KATUiliAril V OF SAN PKDKd, 59 



San Diego Mem — Pliocene. — The Sail Diogo mesa is composed of Pliocene 

 strata. Outcrops of the soft yeHow and brown Pliocene sandstone occnr in niunv 

 places in the northern part of the cit}'. A good exposure is found at the north end 

 of Tenth street, a short distance northwest of the Russ school, where a cut on both 

 sides of a small ravine reveals a section of the Pliocene about fifty feet thick. Phis 

 exposure is oidy about two hundred feet north of the "San Diego well," which was 

 dug about twenty years ago, and which has become famous through the discussion 

 of the age of the fossils which were taken from it. Mr. llemphill, who obtained the 

 fossils from this well during its excavation, informed the writer that fossiliferous strata 

 were penetrated to a dejith of one hundred and forty-nine feet. As the exposure of 

 the San Diego formation above the mouth of the well is fifty feet thick, the fossil- 

 bearing strata of the Pliocene formation of the San Diego mesa are at least two hun- 

 dred feet in thickness. The di[) of the strata above the well is nouth, or toward the 

 bay, at an angle of eight or ten degrees. 



2\ceiUy-sixth i>(ree( — Fkislocene. — ^A blnfY about eighteen feet high rises from 

 the edge of the bay at the foot of Twenty-sixth street, San Diego, and extends for 

 two or three blocks both towmd the east and toward the west from Twenty-sixth 

 street, forming the shore line along this part of the bay. At the base of this blulT, 

 and covered by the water at high tide is a stratum six inches thick made up almost 

 entirely of the upper valves of Annmia limatnla. No right valves were found in this 

 deposit, and this species seemed to be restricted to this layer. A stratum of fine, 

 yellow fossiliferous sand, four or five feet thick, rests upon the Anomia beds; and 

 above the fossiliferous bed is about twelve feet of fine brown sand, overlain by sandy 

 soil. Dosinia pouderosa, Ca/lista neiccombiaiia, Mactra californica, and Cardium pro- 

 cerutii are the predominating species in the yellow sand stratum. The fauna of this 

 locality is equivalent to that of the upper San Pedro series at San Pedro. 



Spanish Bight — Pleistocene. — The Coronado peninsula is a long, low, narrow 

 .sand-spit lying between San Diego Bay and the ocean. Near its western end is a 

 small inlet on the bay side, known as Spanish Bight. The western shore-line of this 

 inlet is a bluff varying in height from twelve to eighteen feet, while the stratum at 

 the base of the bluff forms the beach, and is covered by the water at high tide. This 

 lowest layer is composed of a firm, fine brown sand in which are imbedded numerous 

 large Atniantis callosa, which have the appearance of living shells, so naturally do 

 they lie on the sand. An attempt to remove thera, however, dispels the delusion, for 

 in most cases they are quite firmly imbedded in the sand layer. 



There are three feet of fine, soft, unfossiliferous gray sand above the Ainiantis 

 layer, and this is overlain by a deposit, varying in thickness from three to five feet, of 

 soft gray sand, which is very fo.ssiliferous near its base and gradually grades into 

 the almost unfossiliferous gray sand a few feet above. About twelve feet from the 

 base of the bluff is a layer from three to six inches thick containing numerous Dona.c 

 lf£vig(ita cemented together. This Donax layer is the uppermost fossiliferous stratum^ 

 the bluff above this being composed of unfossiliferous sands. The fauna of the 

 Spanish Bight deposits is similar to that of the upper San Pedro series at Los Cerritos, 

 and the deposits are probably of contemporaneous origin. 



