330 CALIFORNIA ACADEMY OF SCIENCES. 



quite a number of species closely resembling species 

 which in eastern America are typical of the Miocene. 

 Two other facts of interest come in here ; first, as already 

 pointed out, the evidence of practically continuous sedi- 

 mentation from the White Miocene shale to the top of the 

 Pliocene or a little beyond; and second, the interesting 

 way in which, as the series is ascended, the older forms 

 drop out one by one. Thus, the large pectens are found 

 only near the very bottom of the series, none of them 

 having been found in the main body of the section as ex- 

 posed on Seven-Mile Beach. In the same way many of 

 the other species can be traced part way up the column, 

 when they disappear, as the Crepidida grandis and large 

 Areas, thus showing finely a gradual dying out of one 

 fauna and replacement by another. 



It would therefore seem that the lowest, or what might 

 be called the Pecten beds, are more closely related to the 

 Miocene, but a rapidly changing fauna soon gives the 

 beds a Pliocene aspect which is maintained through most 

 of the section. The writer has, therefore, thought it best 

 to call the lower beds, as exposed along the coast south 

 of Half Moon Bay and at Capitola, " Transition Beds." 



On Seven-Mile Beach the great thickness of strata gives 

 a splendid opportunity for the study of faunal changes. 

 On account of the friable nature of most of the specimens, 

 the lists given are very incomplete. The suggestion has 

 been made that the top of the Merced series on Seven- 

 Mile Beach extends into the Pleistocene. To show the 

 ground for such a belief the fauna of the strata from the 

 "upper gasteropod bed" upward is given separately, the 

 fossiliferous strata above the upper gasteropod bed espe- 

 cially having a Pleistocene aspect, all the forms of which 

 still live on the coast. 



Of the forms given, the Ne^titnea tahulata, Caly^trcBa 



