P I. A T K X X . 



:\Il(K'i;.\F, AND I'LIOCKXK I'I'X'TKNS. 



[Unless otherw ISO stnlccl all rijjiires are appruximatcly natural sizt'.] 



Page. 



Fill. 1. Prrlni ( Liinij„'i-lni ) ,-slr<'lliii(iis (.'miiail. U. S. M. M. 1331 7. ('otyiiu 74 



Exterior of portion of iinperft'ct right valve; altitude 90 nun. .Santa JIargarita formation 

 (upper Pliocene), fctrella valley, San Lnis Obi.opo C'onnty, Cal. CM. B. ) 



Fi(i. 2. Pecti'ii {Ltjropi'rten) estrdlcmis Conriit\. ('. S. M. B. 12871 74 



Kxterior of very convex right valve (form described as P. roln/oniiis Conrad); altitude 

 71 mm. San Pablo formation (upper Miocene), Coalinga, Fresno County, Cal. I M. B. ) 



Fio. 2ii. Same specimen as fig. 2 74 



I'rotile of right valve viewed from rear. (M. P.) 



Fio. 3. Perlen estrellaiiits Conrad var. nitaliii:r n. var. I>. A. Type 7t> 



Ivxterior of imjierfect right valve; altitude 6S nun. I'pper Miocfue, near Isthmus, Santa 

 Cataliiia Island, Los Angeles County, Cal. (M. B. ) 



Fio. 'All. Same speriuien as llg. 3 "6 



I'rolilc- of right valve viewed from the rear. {'SI. P.) 



Fii;. 4. Piiii'ii i\<li-iUitiiiis Conrad var. nitiiliii:i n. var. I). A 76 



Interior showing undio and hinge; liinge line .30 mm. Same locality as tig. 3. (M. B. ) 



184 



