GEOLOGIC RECONNAISSANCE IN BAJA CALIFORNIA 741 
were determined by Dr. Julia A. Gardner, who regards them as 
probably Upper Miocene. 
Fossils collected near the top of Cerro Angel, 18 miles west of 
San Ignacio, were identified as follows: Oliva-sp.; Turritella, cf. 
hoffmant Gabb; Calypiraea, cf. diegoana Conrad; Glycymeris sp.; 
Arca sp.; Pecten n.sp.; Pecten sp.; Dosiniaarnoldt Clark: Chione 
elsmerensis English?; Chione sp.; and Macoma vaulecki Arnold. 
They are regarded as San Pablo or late Miocene. 
These yellow beds outcrop extensively under the Java mesas 
about San Ignacio (see Fig. 14) and in the arroyo below that 
village. Fossil oysters are abundant in some of the layers. 
Yellow beds similar to those of the La Purisima region over- 
lie Monterey beds in the slopes east of Rancho Tepetate. The 
steeply uplifted strata just northwest of Rancho Platana include 
a richly fossiliferous limy ledge which yielded fossils of the same 
fauna as those occurring in the basal hmestone member of the yellow 
beds in the Arroyo de la Purisima. The following were identified 
by Dr. Julia A. Gardner: Strombos n.sp. (same as one at La Puri- 
sima); Zurritella n.sp. 1 and 2; Codakia sp.; Cardium sp. ind.; 
chione sp., ci. C. fernandoensis English; C. sp. ind. and Psephidea ? 
sp.—a Carrizo Creek fauna. It is reported that later Miocene 
beds outcrop on the gulf shore near Cayote Point and Agua Verde 
Bay, doubtless coming up from under the agglomerate series, as 
shown in section 4. 
From a bed in the base of the formation or not far below it, 
8 miles northwest of El Pilon, were collected the following fossils: 
Turritella sp., cf. T. margaritana Normand; Turritella N. sp.; 
Yoldia sp.; Ostrea sp. ind.; Mytilus? sp.; Modiolus? sp.; Pecten? 
sp., Chione sp., ci. C. fernandoensis English and Mactra? sp.; deter- 
mined by Dr. Julia A. Gardner who regards them as late Miocene 
or early Pliocene. 
MESA SANDSTONE AND THE GREAT LATER TERTIARY VOLCANIC SERIES 
Gabb recognized the fact that the widespread mesas of southern 
Baja California consist of a thick mass of west-dipping sediments 
and conglomerates. He named it the ‘‘mesa sandstone,” and 
while he erroneously extended the application of the name to other 
