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Vol. VIII] DUMBLE— GEOLOGY TAMPICO EMBAYMENT AREA 149 



Echinoderms r^ 



Clypeaster concavus Cotteaii 



" sp. a Dickerson & Kew 



sp. b 

 Eupatagus, sp. 



Lovenia dumblei Dickerson & Kew 

 Macropnetistes mexicannm Dickerson & Kew 

 Schizaster scherzeri Gabb. 

 Mollusca :" 



Ostrea, sp. 



Pecten gatunensis Toula 



" oxygonum-optimum B. & P. 

 Turritella altilira Conrad 



Tuxpam 



Following the clays, shales, and limestones of the San 

 Rafael, we find another series of clays and shales which is also 

 very fossiliferous in places as in the vicinity of Tuxpam, which 

 place gives them their name. 



The Tuxpam beds comprise yellow clays and sandy clays, 

 blue sandy shales and bands of calcareous sandstone. For the 

 most part, the beds seem to lie nearly flat and show little dis- 

 turbance, even in the vicinity of volcanic necks. 



They are well exposed around San Fernando, on the Con- 

 chos River, have not been definitely identified at Tampico, but 

 form a large part of the surface material around Tuxpam and 

 southward to Larios and Nautla. While the contact of the 

 Tuxpam and San Rafael beds has not been positively observed, 

 we may conclude that a decided unconformity exists because 

 there are numerous small anticlinals to be seen in the San 

 Rafael, while the Tuxpam beds seem to show little or no dis- 

 turbance of this character. A further study will probably dem- 

 onstrate that south of the Otontopec divide the Tuxpam beds 

 overlap the San Rafael in many places, as they certainly do in 

 the region north of Tordo Bay. 



While certain molluscan forms seem to be common to the 

 San Rafael and the Tuxpam, the number of species occurring 

 in the Tuxpam is very much greater. The echinoderms of the 



" Determinations by Dickerson & Kew. 

 "^ Determinations by Dickerson & Kew. 



