1916] Martin: Pliocene of Middle and Northern California, 243 



The following species were obtained from the upper standstone 

 member of the Purisima Formation, chiefly from the sea-cliffs south 

 of Ilalfmoon Bay : 



Echinodermata 



Echinaraclmius gibbsii Remond 

 Scutella interlineata Stimpson 

 Scutella perrini Weaver 



Pelecypoda 



Acila castrensis Hinds 

 Acila rectus Conrad 

 Area canalis Conrad 

 Area trilineata Conrad 

 Cardium meekianum Gabb 

 Clidiophora punctata Conrad 

 Cryptomya californica Conrad 

 Cryptomya ovalis Conrad 

 Dosinia ponderosa Gray 

 Leda taphria Dall 

 Macoma calcarea Gmelin 

 Macoma inquinata Deshayes 

 Macoma nasuta Conrad 

 Marcia oregonensis Conrad 

 Panomya ampla Dall 

 Panope generosa Gould 

 Paphia staleyi Gabb 

 Paphia tenerrima Carpenter 

 Pecten healeyi Arnold 

 Pecten nutteri Arnold 

 Pecten oweni Arnold 

 Pecten purisimaensis Arnold 

 Phacoides annulatus Reeve 

 Schizothaerus nuttalli Conrad 

 Schizothaerus pajaroanus Conrad 

 Siliqua nuttalli Conrad 



Solen sicarius Gould 

 Spisula albaria Conrad 

 Spisula catilliformis Conrad 

 Spisula hemphilli Dall 

 Thracia trapezoidea Conrad 

 Yoldia cooperi Gabb 

 Zirphaea gabbi Tryon 



Gasteropoda 



Argobuccinura oregonensis Redfleld 

 Astyris richthofeni Gabb 

 Bathytoma carpenteriana Gabb 

 Bittium asperum Gabb 

 Calyptraea fllosa Gabb 

 Calyptraea inornata Gabb 

 Chrysodomus liratus Martyn 

 Chrysodomus portolaensis Arnold 

 Chrysodomus purisimaensis Martin 

 Chrysodomus stantoni Arnold 

 Chrysodomus tabulatus Baird 

 Crepidula, cf. onyx Sby. 

 Crepidula princeps Conrad 

 Drillia mercedensis Martin 

 Miopleiona oregonensis Dall 

 Nassa moraniana Martin 

 Nassa mendica Gould 

 Natica lewisii Gould 

 Natica clausa Brod. & Sby. 

 Thais lamellosa Gmelin 



Cirripedia 



Balanus, sp. 



This list contains a few forms, such as Pecten healeyi Arnold, 

 and Pecten purisimaensis Arnold, which are supposed to be charac- 

 teristic of the Pliocene, and have not so far been reported from the 

 Merced Series at the type locality. This, together with the fact that 

 certain supposedly Miocene forms, Pecten oweni Arnold, Pecten nut- 

 teri Arnold, and Echinarachnius gibbsii Remond, occurred in this 

 formation, was the basis upon which Arnold and Haehl separated 

 these beds from the Merced Series and applied the new name Purisima 

 Formation. The presence of a number of the larger pectens has 

 caused some palaeontologists to place the beds as intermediate be- 

 tween the Pliocene and Miocene, and still others to place them entirely 

 within the Miocene. It is a well-recognnized fact that the division 

 between the Miocene and Pliocene in California is not well marked 

 in any of the formations, and any separation attempted, outside of 

 that suggested by the faunas, is more or less arbitrary. It is not the 

 object of this paper to make an accurate age determination, but 



