ON A NEW AMMONITE FAUNA OF THE LOWER TURONIAN 



OF MEXICO 



BY EMIL BOSE 



I 



INTRODUCTION 



A number of years ago the existence of Turonian beds was proven in 

 Mexico and later on it was shown that these beds have a great distribu- 

 tion in the country. At first very few localities with faunas of this age 

 were known, but later the finds of fossils of Turonian age have augmented 

 in such a manner that we now know that the Turonian has a vast dis- 

 tribution in Mexico, numerous localities having been discovered between 

 Lat. 2030' N. and Lat. 32 N. All of these beds are petrographically 

 very uniform and consist of argillaceous shales and laminated limestones 

 with intercalations of thin beds of limestone, all of black to light gray 

 color. The fauna of these beds is also rather uniform and consists mostly 

 of numerous specimens of Inoceramus labiatus Schlotheim, in some places 

 accompanied by Inoceramus hercynicus Petraschek ; in some localities fishes 

 are relatively numerous ; in others bivalves other than Inoceramus are 

 found. Cephalopods have been found very rarely, all of them crushed 

 and nearly indeterminable. The determination of the age had to be 

 founded exclusively on the Inoceramus and on the position of the beds 

 in relation to the Senonian and the Cenomanian. 



About nine years ago I received the first collections of Turonian am- 

 monites, which allowed a much better determination of the age of the 

 beds mentioned here because these cephalopods were found together with 

 well preserved specimens of the same Inoceramus which already had been 

 determined by us as 1. labiatus. 



In February, 1911, Dr. Ernst Angermann sent me a email collection 

 of fossils collected by him on the Cerro del Macho, Hacienda del Moh6vano, 

 Municipality of San Pedro, District of Parras in the State of Coahuila. 

 The greater part of these fossils consisted of internal molds of bivalves 

 and gastropods, but there were also present three cephalopods relatively 

 badly preserved and several indeterminable fragments of ammonites. I 

 recognized at once that these fossils belonged to a facies and a horizon 

 altogether unknown in Mexico, one of the ammonites being a Vascoceras 

 of the group of V. Kossmati and another a Neoptychites of the group of 

 N. xetriformis Pervinquiere, the bivalves belonged mostly to Trigoniu, 



