Vol. IX] SMITH— CLIMATIC RELATIONS 145 



more northerly Wildcat formation. Of the entire fauna about 

 35% are extinct and 65% living. It is commonly regarded as 

 upper Pliocene, but belongs to the older horizon of that division. 

 The temperature of the sea in which the Merced beds were laid 

 down was probably about 50° F., instead of 55° F. at present. 



Purisima (Half Moon Bay, on the San Francisco Peninsula, 

 lat. Z7° N.). Area trilineata Con., Cardium meekanum Gabb, 

 Chione securis Shum., Glycimeris coalingensis Arn., Macoma 

 calcarea Gmel., Macoma middendorM Dall, Marcia oregonensis 

 Con., Mya truncata L., Panomya ampla Dall, Panopea gencrosa 

 Old., Paphia staleyi Gabb, Pecten purisimaensis Arn., Peroni- 

 dea lutea Gray, Phacoides anmdatus Rv., Schizothoerus pajaro- 

 anus Con., Spisida albaria Con., Spisida voyi Gabb, Thracia 

 trapesoidea Con., Yoldia cooperi Gabb, Zirphea gabbi Tryon, 

 Argobuccinum oregonense Redf., Bathytoma car pent eriana 

 Gabb, Chrysodomus colmaensis Martin, Chrysodomiis imperl- 

 alis Dall, Chrysodomus liratus Martyn, Chrysodomus portolor- 

 ensis Arn., Chrysodomus purisimaensis Martyn, Chrysodomus 

 stantoni Arn., Chrysodomus tabulatus Baird, Crepidida prin- 

 ceps Con., Gyrineum marshalli Reagan, Miopleionia oregon- 

 ensis Dall, Nassa moraniana Martin, Natica clausa B. & S., 

 Natica draconis Dall, Natica leivisii Gld., Dendraster inter- 

 lineatus Stimp. (all northern types, or characteristic of this 

 latitude); and: Area canalis Con., Chione elsmerensis Eng., 

 Dosima ponder osa Gray, Pecten healeyi Arn., Pecten 

 nutteri Arn., Pecten purisimaensis Arn., Pecten oweni Arn., 

 Dendraster ashleyi Arn., Dendraster perrini Weaver, (all 

 southern types). 



This fauna shows a mixture of southern and northern types, 

 with the latter predominating, the giant Chrysodomus, espe- 

 cially, indicating cooler water. Dosima ponderosa,Arca canalis, 

 and Chione elsmerensis indicate warm water. The temperature 

 was probably a little warmer than the present, approximately 

 60° F., since northern forms can and do range southward by 

 increasing their depth, while southern forms can not range 

 north of their normal temperature. 



Of the whole fauna 46% are extinct, and 54% living. 



Santa Clara lake beds. These freshwater beds are known at 

 many localities around the Santa Clara Valley, south of San 

 Francisco. They contain a small fauna of bivalves and gastro- 



