252 PROCEEDINGS OF THE CALIFORNIA 



[but those which have been obtained, are too imperfect for recognition ; they 

 were referred to Mr. Meek for examination. j. d. w.] 



At San Marcos, between San Antonio de la Huerta and the Real Viejo, 

 metamorphic jaspery slates occur in connection with the carboniferous lime- 

 stones; they are probably of Triassic age. Gold is found in the gulches be- 

 tween the quartzite ridges, as in the Canada de la Higuera, near Los Bronces^ 

 in the Canada de la Iglesia, between the latter place and San Antonio de la 

 Huerta, and generally where the quartzites occur. 



Jurassic (?) Rocks. 



In the eastern part of the Magdalena and Altar districts, are valleys with 

 low hills and ridges of auriferous clay slates, with interstratified beds of por- 

 phyry and diorite. Localities of these rocks are Cerros de la Barajita, between 

 Querobabi and Santa Ana ; Cerritos de la Tierra Colorada, where the forma- 

 tion contains beds of variously colored limestones, entirely made up of fossils, 

 South of La Magdalena this formation rests on metamorphic sandstones and 

 shales. [The reasons for referring these rocks, with doubt, to the Jurassic form- 

 ation, have been already given ; see page 24(5.] 



Cretaceous Rocks. 



In the Sahuaripa Valley, four miles east of Arivechi. and seventy-two leagues 

 northeast of Guaymas, is a locality of Cretaceous Fossils of great interest. The 

 hill in which they occur is called " Cerro de las Conchas," or " Shell Mount- 

 ain." The rocks exposed are unfossiliferous strata of coarse-grained sandstone 

 at the base, overlain by clay shales and argillaceous limestone filled with fossils, 

 The exposure is very limited in extent : the shales are a few hundred feet thick, 

 and they dip to the east, as do also the beds of carboniferous limestone on which 

 the Cretaceous deposits rest. Masses of porphyry crop out from under the 

 shales, without there being any peculiar indication of metamorphism or dis- 

 turbance in their vicinity. Other patches of shelly rock are said to occur in the 

 valley on the eastern side, at the foot of the sierra. [A small lot of fossils 

 collected here by M. Remond were referred to Mr. Gabb for examination ; and 

 since that, a considerable number of additional specimens have been received, 

 but have not yet been investigated. Several species were identified as already 

 described from Texas, and figured by Rocmer in " Die Kreidebildungen von 

 Texas ;" these are, Ammonites pedernalis, von Buch ; Natica pedernalis, Roem. ; 

 TumteUa seriatim-granulata,~Roem.; Gnjphaa navis, Hall ; Cijp/iosoma Tex- 

 amim, Roem. ; Eulima Texana, Roem. Besides these, two other species are 

 identified, namely; Cardium midtistriatum, Shum., and - Turbindia Texana, 

 Con. 



There is a considerable number of new species. among the specimens from 

 this locality, among which the following genera are represented : Turritella, 

 Chemnitzia, Avellana, Cardium, Trigonia, Panopaa, Pinna, Cucullcea, etc. 

 These will be described and figured by Mr. Gabb, who also remarks that the 



