258 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
As a further proof of the fact that the continental land masses were 
large and extensive during the Jurassic period, we have the indisputable 
testimony that on the Pacific coasts of both the North and South 
American continents there is an extensive development of fossiliferous 
marine littoral Jurassic beds, which grade up without break into the 
Cretaceous formations of the Pacific province which were deposited 
against a land barrier. 
Furthermore, it is very probable that the Pacific shore lay much 
farther to the eastward during this period than at present, for, as will be 
shown in our discussion of the Cretaceous, beds of Pacific sedimentation 
occur in the Mexican peninsula at Catorce, far eastward of the present 
Pacific shore line. "These beds were undoubtedly derived from an east- 
ward lying land, and the Pacific at the beginning of the Cretaceous 
epoch covered a large portion of the Mexican region. 
Fossiliferous Jurassic beds are now known to occur on the western 
or interior side of the Eastern Cordilleras in Mexico and Trans-Pecos, 
Texas, at Catorce, as noted by Aguillera, Miquehuana and Monterey, as 
seen by the writer, and at Malone, Texas, as recently reported by 
Cragin. The oceanic affinities of these beds are as yet unpublished, but 
geographically they belong to the great interior basin region, and not 
the Atlantic slope. 
A. Agassiz has shown that the deep-sea echinoid fauna of the Carib- 
bean and Gulf of Mexico contains a mixture of Mesozoic Pacific types. 
This fact may suggest that there was an oceanic passage across Central 
America in Jurassic time, and that the continental bridge, if it existed, 
may have then been in the Windward region. The discussion of this 
conjecture, however, must be postponed until a future paper. 
The Cretaceous. — The records of the Cretaceous period also present 
evidence which suggests a possibility of the existence of a complete land 
barrier between the two oceans. The Cretaccous rocks are highly fos- 
siliferous, and are the first in ascending series affording sufficient pale- 
ontologie data upon which to base a discussion of the past relations of 
the two great oceans. 
Discordance of the Faunas of the Atlantic and Pacific Provinces. — Active 
research of recent years has resulted in the conclusion that, of the many 
hundred species occurring in the large faunas of the Lower and Upper 
Jretaceous sediments of the Atlantic and Pacific provinces of the United 
States, not one species has been found in common with the faunas of the 
two, oceans. So marked is this difference that it is the most impressive 
fact which has been encountered by recent students of these forma- 
