LATER MESOZOIC INVERTEBRATE FAUNAS 185 



connect it with the Jurassic of the South American Cordillera. He 

 concludes that there must have been direct marine connection with 

 all these regions. The most striking example of the introduction of a 

 new element in the fauna is the intercalation of a thin Aucella bed in 

 the midst of strata containing the Mediterranean type of fauna in 

 the upper Kimmeridgian. The Aucella must have come in from the 

 Pacific where, as we have seen, the boreal type of fauna extended at 

 least as far south as middle California. The nearest recorded occur- 

 rences of Aucella in the other direction are on the east coast 

 of Greenland and in England. On the other hand this Mexican 

 fauna as a whole is so unlike that of California and so related to 

 that of Europe, and the geographic position of the beds is such 

 that connection with the Gulf of Mexico seems most reasonable. 

 The area should therefore be mapped as included in the Atlantic 

 sedimentation though it is probable that the Pacific waters bearing 

 the Aucella found temporary access to it from some point south of 

 the Gulf of California. If the exact position of this temporary 

 Pacific connection is still indicated by sediments they have not yet 

 been recognized. 



Farther south in Mexico a somewhat different facies of the Upper 

 Jurassic fauna found in the state of Oaxaca has been described by 

 Felix' but according to Cragin^ this has some species in common with 

 the Malone Jurassic fauna of western Texas which on the other hand 

 shows some relationship with the fauna of Catorce, San Luis Potosi, 

 and hence also with that of Mazapil. The Malone fauna shows no 

 connection whatever with the Rocky Mountain Jurassic because it 

 belongs to a later stage and to a different province. It probably 

 lived in an arm of the Gulf of Mexico directly connected with the area 

 in Zacatecas and San Luis Potosi, and including the locality near 

 Cuchillo Parado, Chihuahua, reported by Aguilera.^ Some of the 

 elements of the Malone fauna show decided Cretaceous affinities 

 and thus strengthen the evidence that it is latest Jurassic. 



In Europe Neumayr recognized three marine faunal provinces 

 in the Jurassic which, as he believed, indicated climatal zones. These 



1 Palaeontographica, Band XXXVII (1891), pp. 172-80. 



2 U. S. Geol. Surv., Bull. 266, 1905. 



3 Apercu siir la geologic du Mexique, p. 8, 1906. 



