2 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.61. 



ever, some thicker bedded layers of shale in the upper part of the 

 formation. The Mendez formation conformably overlies the San 

 Felipe formation, and in this part of Mexico consists of about 800 

 feet (250 meters) of calcareous shale or marl ranging in color from 

 gray or greenish gray through pale pink to rather strong red. The 

 thickest and most persistent bands of red are in the upper part of the 

 shale. The dividing line between the Mendez shale and the under- 

 lying San Felipe limestone has been arbitrarily taken to be the top 

 of the uppermost layer of limestone, but there are some rather thick 

 layers of Mendez-like shale interbedded with thinner beds of lime- 

 stone below this uppermost limestone layer. The Mendez shale is 

 uncomformably overlain in the easternmost part of Chocoy hacienda 

 by marine strata of Tertiary age. 



The topography in the vicinity of Manuel and Chocoy stations is 

 rather strongly rolling and prairie-like, and the surface is drained 

 by arroyos which are dry except during rainy periods. The fossilif- 

 erous outcrops examined were in the beds and banks of these ar- 

 royos, in gullies, and in railroad cuts. Most of the fossils collected 

 on my first visit w ere found loose in the beds of the arroyos, but some 

 of them contained attached portions of matrix, which showed them to 

 have been derived from the shale and limestone cut by the arroyos, 

 and some fragments of Inoceramus and Ostrea were found definitely 

 in place in the shale. Subsequently Mr. Bishop found crinoid stems 

 in place in layers of San Felipe limestone at two localities, and he 

 also found in the Mendez shale the colony of rudistids described on 

 pages 6 to 8 as Tampsiu bisJwpi. Mr. Beckley and the writer also 

 found the colony of rudistids described on pages 8, 9 as Tampsia cho- 

 coy en sis virtually in place in the Mendez shale. 



THE FOSSILS AND THEIR SIGNIFICANCE. 



The fossils found in the upper part of the San Felipe formation on 

 Las Flores and Chocoy haciendas include : Foraminifers ; an organ- 

 ism whose zoological affinities have not yet been determined, perhaps 

 a hydroid or a coral; stems of crinoids belonging to the genus 

 Balanocrinus in the family Pentacrinidae ; an undescribed brachio- 

 pod ; numerous fragments of the shells of one or more large species 

 of Inoceramus; Ostreaplumosa Morton; Ostrea congesta Conrad( ?) ; 

 representatives of the family Radiolitidae, including Sauvagesia 

 degolyeri Stanton (?), Durania manuelensis Stephenson, and poorly 

 preserved fragments probably representing several other species of 

 Saiwagesia. 



Outside of these haciendas fossils were found in the San Felipe 

 limestone at two localities in the State of Tamaulipas. One of these 

 was on the road leading from Ciudad Victoria eastward to Soledad, 



