During spring and summer of 1915, an expedition was sent to the peninsula of Lower California (Baja California) by a Swiss Colonization Company. The scientific work was under the direction of the writer, who enjoyed excellent assistance from his friends Prof. Dr. Ad. Hartmann, of Aarau, and Top. Eng. E. Kluth, of Zurich. Although little time was available for stratigraphic studies, some of our observations of that almost unknown country seem to be worthy of publication.

It is intended to give in the present paper the results of the writer's collecting in the Lower Liassic (Carixian = Lower Pliensbachian) Ammonite Beds of the Island of Pabay (Pabba), known to fame since MacCulloch and Hugh Miller drew attention to the abundance of its fossils and Murchison and A. Geikie collected its ammonites. Some of these were many years ago described by Sowerby and Wright, and in the more recent Survey Memoir1 a list of fourteen ammonite species was given, a number trebled in the present account. Unfortunately, the hundred feet or so of micaceous, metamorphic shale at Pabay is cut up by “dolerite and basalt dykes and sills” to such an extent that the tracing of the succession is not an easy matter.