124 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Se». 



He says that it ''consists of hard gray, pure, compact porce- 

 lain-like limestone bedded in layers less than a foot thick and 

 is characterized in its upper part by the occurrence of an abun- 

 dance of black to dark gray and green chert nodules interbedded 

 with the limestone The uppermost member of the lime- 

 stones which are massively bedded in the northern Veracruz 

 and Valles region are somewhat porous and contain great solu- 

 tion caverns." 



From this I understand that he considers the uppermost 

 member, or Rudistes limestone of the Tamasopa, missing in 

 this region, in which case these beds may be related to the 

 Maltrata limestone of Bose's Orizaba section. 



The Orizaba limestone (Meso-Cretaceous) of Bose consists 

 of two divisions: The Maltrata or lower member and Es- 

 camela or upper. He describes them as follows : 



"The Maltrata limestones constitute an important division, 

 which is often of great thickness. The greater part is com- 

 posed of limestones in thin beds, is without fossils, and of a 

 clear dark gray or black color. The limestones contain numer- 

 ous segregations of flint in the form of lenses. In the upper 

 portion the flint occurs in the form of nodules and irregular 

 bodies. In the lower part of the limestones there occur in 

 many places intercalated argillaceous slates which are yellowish 

 and lustrous like silk, but these never form heavy beds. In the 

 upper part toward the boundary with the Escamela limestones, 

 there occur gray limestones and dolomites in heavy beds in 

 which the stratification is scarcely recognizable. Above these 

 follow dark compact limestones which represent the passage 

 to the Escamela limestones and which may better be considered 

 a part of the latter. In some places there occur above the 

 dolomites flinty limestones, and in that case the line between 

 them and the Escamela limestone is sufficiently well marked. 



"The Escamela limestones are composed of a clear gray to 

 a dark gray limestone, in some places but slightly stratified 

 and elsewhere in clearly distinct beds. Cherts occur only in the 

 lower portion. There are no intercalations of slates or marls. 

 The limestones resemble in their characters very often the 

 Cretaceous limestones of southern Italy. They are petrograph- 

 ically very uniform and may be recognized with ease." 



Still farther south in Chiapas he describes the Meso-Cre- 

 taceous beds thus : 



