MARINE JURASSIC ROCKS IN SOUTHWESTERN TEXAS 819 
limited area of Jurassic rocks in northern Mexico, not far south- 
west of Saltillo. This is apparently the nearest known occur- 
rence of marine Jurassic rocks to that here announced, being dis- 
tant from Malone some 500 miles in a southeasterly direction. 
The discovery of Jurassic rocks in El] Paso county, Texas, there- 
fore, raises the interesting question whether other limited areas of 
Jurassic may not yet be discovered in intermediate territory. 
This article in major part, including definite reference of the 
fossiliferous beds of the Malone hills to the Jurassic upon evi- 
dence derived from the Trigonias of the Goodell collection, was 
first written in the latter part of 1896. Its publication was post- 
poned, — with some revision of the manuscript in the meantime, 
—in the hope that I might soon visit the formation in person 
and secure more abundant data. This I was unable to do till 
August last. Reaching the vicinity on the nineteenth of the 
month, I spent about three weeks exploring some of the locali- 
ties accessible from Sierra Blanca station, devoting principal 
attention to the Malone fauna and formation. The large col- 
lection of fossils made from the latter, so far as yet studied, con- 
firms the reference to the Jurassic. I at first intended to incor- 
porate the results of this trip with those derived from the Texas 
Survey and Goodell collections and data ; but it has seemed best 
to publish deductions from the earlier data without the further 
delay involved in the study of this season’s material, and to pre- 
sent the results of the latter study, when completed, in separate 
articles. 
When this article was first written, I did not have access to 
the first number of the Boletin de la Comision Geologica de 
Mexico, containing Castillo and Aguilera’s ‘‘ Fauna Fosil de la 
”) 
Sierra de Catorce,’’ my copy of it having been temporarily lost 
in the exigencies of a change of residence. The missing docu- 
ment has since come to light, and the independent reference 
which I have made of the Malone fauna to the Jurassic, is con- 
firmed by it, Plewromya inconstans and Lucina potosina being appar- 
ently common to the Malone and the Alamitos (‘upper 
Jurassic”) formations (as elsewhere indicated in footnotes), and 
