Dcscrij'tions of Species. 23 



Ostrea franklini Corjnand. 



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

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

 plate V, figs. l-18rt; plate vi, figs. 19-25 ; plate vii, figs. 28-30. 



Tlie general aspects and variation of tins characteristic oyster 

 of the Trinity Division have lieen fully descrihed and figured in 

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

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

 extensive study of the occurrence of the specimens in >iitu^ still 

 helieves 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. 



Clioffatf figures and descriljes from Portugal 0. harrosei, a form 

 which resembles a variety of O.franJdiiii found at Glen Rose. 



This species occurs in great al)undance throughout the Trinity 

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

 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 tliat none of the true Gri/p/i;raf< or 

 Exogyras have yet l)een found in the Trinity Division. 



Ostrea franklini ragsdalei var. nov. 



Plate I, Fig. G. 



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

 tudinal coshe; l)eak 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. frdnldini 

 Co(juand, but the larger valve is much more round, the point 

 more prolonged and characterized by the strong costa; which do 

 not ap[)ear upon tlie adult specimens of the 0. fraidiiiii c\se- 

 where found. 



* American ( Jef)lo(j;ist, vol. iv, I)ecem])er, 1889, pp. 359, oGO. 



tlveoneil de Monorjraphios Stratisnipliiques Sur le Systeme Crctariiiue 

 <lu Portugal, par Paul ChoH'at. Lij-lwn, T8S5, p. ;]7, plate iii, fitrs. 7, 8, 9, 

 10, 11, IL'. 



