1916] Nomland: Invertebrate Zones of Jacalitos and Etchcgoin 81 



ridge in the outermost foothills. At one locality about fifty feet below 

 the upper shale band a bed of porous, white, fine-grained tuff with a 

 small quantity of interstratified quartz sand was found. In the upper 

 half of the formation, on approaching the anticline from the north, 

 several other shale members together with additional invertebrate 

 zones make their appearance. In this region relatively little vertebrate 

 material is present. This may perhaps be due to deeper water here 

 than farther north during deposition. 



No invertebrate fossils have thus far been found in the seventeen 

 hundred feet of sands, gravels, and clays mapped as Jacalitos. Strati- 

 graphically, however, these beds seem to form a continuous, conform- 

 able series, at least from Arnold and Anderson's basal gravels, up to 

 the unconformity above the Glycymeris zone. This zone can be traced 

 almost continuously for nine or ten miles. About forty feet above it 

 another zone appears at intervals. South of Oilfields for a short dis- 

 tance Glycymeris eoalingensis Arnold is found in great abundance. 

 On going north, however, Tamiosoma, cf. gregaria Conrad and Mulinia 

 densata Conrad are the more common species. 



The invertebrate fauna of the Glycmeris zone and the one a short 

 distance above it consists of the following species : 



Invertebrate Faunae Zones 



ECHINODERMATA 



Eehinarachnius gibbsii Eemond 



ClRRIPEDIA 



Balanus, sp. 



Tamiosoma, cf. gregaria Conrad 



Pelecypoda 



Area trilineata Conrad 

 Cardium corbis Martyn 

 Cryptomya ovalis Conrad 

 Cryptomya quadrata Arnold 

 Glycymeris eoalingensis Arnold 

 Glycymeris septentrionalis Mid- 



Margarita johnsoni Arnold 

 Panopea generosa Gould 

 Paphia staleyi Gabb 

 Peeten wattsi Arnold 

 Pecten oweni Arnold 

 Peeten estrellanus Conrad, var. 



dendorf 

 Macoma inquinata Deshayes 

 Macoma nasuta Conrad 

 Macoma secta Conrad 

 Metis alta Conrad 

 Modiolus, sp. 

 Mulinia densata Conrad 

 Mytilus eoalingensis Arnold 

 Ostrea atwoodi Gabb 



terminus Arnold 

 Phacoides, sp. 



Sanguinolaria nuttalli Conrad 

 Saxidomus nuttalli Conrad 

 Schizothaerus nuttalli Conrad 

 Solen sicarius Gould 

 Spisula albaria Conrad 

 Spisula eoalingensis Arnold 

 Tellina bodegensis Hinds 



