Descriptions oj Species. 23 



Ostrea fraiiklini Coquand. 



Monographic du Genre Ostrea, p. 58, plate xxiii, figs. 8-10. 

 Hill, Arkansas Geological Survey, Annual Report 1888, vol. n, 

 plate v, figs. l-18a; plate vi, figs. 19-25 ; plate vii, figs. 28-30. 



The general aspects and variation of this characteristic oyster 

 of the Trinity Division have been fully described and figured in 

 my Arkansas report. Professor Marcou in a review of this work* 

 has divided the form into many species, but the writer, from his 

 extensive study of the occurrence of the specimens in situ, still 

 believes in the unity of the species, although in Europe it has 

 doubtless been the custom of earlier paleontologists to make 

 many species out of variations. 



Choffatf figures and describes from Portugal 0. barrosei, a form 

 which resembles a variety of 0. franklini found at Glen Rose. 



This species occurs in great abundance throughout the Trinity 

 Division, especially at the plant beds near Glen Rose, at the base 

 of the Glen Rose beds in the Colorado section, and in a similar 

 horizon throughout the Glen Rose beds in Arkansas and in 

 Texas. 



It is interesting to note that none of the true Gryphxas or 

 Exogyras have yet been found in the Trinity Division. 



Ostrea franklini ragsdalei var. nov. 

 Plate I, Fig. 6. 



Shell acuminate, oblong, marked by numerous, regular longi- 

 tudinal costa); beak of large valve prolonged, costate, sub-cylin- 

 drical. 



Several incomplete specimens of the larger valve of this spe- 

 cies were procured from the fauna at the plant bed near Glen 

 Rose. The outline is somewhat similar to that of 0. franklini 

 Coquand, but the larger valve is much more round, the point 

 more prolonged and characterized by the strong costa3 which do 

 not appear upon the adult specimens of the 0. franklini else- 

 where found. 



* American Geologist, vol. iv, December, 1889, pp. 359, 300. 



t Rceueil do Monographies Stratigrapliiques Sur le Systeme Cretacique 

 du Portugal, par Paul Choffat. Lisbon, 18S5, p. 37, plate iii, figs. 7, 8, 9, 

 10, 11, 12. 



