Descriptions of Species. 29 



idiu, with the exception of Diceras, a Jurassic form, and is abun- 

 dant in the Ncocomian formation of Spain, France, and Portugal. 



Monopleura marcida and M. pinguiscula White. 



Bulletin U. S. Geological Survey, No. 4, p. 8, plate 5, figs. 1-8. 



Casts and moulds of Monopleura occur in great abundance in 

 the Colorado section, especially at the base of Mount Bonnel, 

 near the mouth of Bull creek. It is impossible to make a cor- 

 rect diagnosis of these, owing to the fact that the smaller valves, 

 so abundant in the Caprina limestone, have not been found in 

 the Glen Rose beds, but there is a general resemblance of the 

 larger valves to the two species named. 



The genus Monopleura^ according to Zittel, has wide distribu- 

 tion in the Lower Cretaceous, occurring in the Neocomian of 

 Provence and the Jura mountains, and seldom ranging higher. 

 In America the genus culminates in the Caprina limestone and 

 is not known later. 



Corbicula arkansaensis Hill. 



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



133, plate ii, fig. 20; plate iv, figs. 3, 3, 6. 



This species was originally figured and described in my Ar- 

 kansas report. It occurs in Pike county, Arkansas, near Mur- 

 ireerfboro, and at the gypsum bluffs of the Little Missouri. It is 

 less abundant in the Texas beds. 



Cardium (?) sevierense Hill. 



[7 Arkansas Geological Survey, Annual Report 1888, vol. n, p. 



134, plate ii, figs. 21, 21d. 



This form has only been found in Arkansas, at the locality 

 from which it was described in my Arkansas report. 



Protocardia sp. indet. 



Small olists, three-quarters of an inch in length, globose; sur- 

 face marking, very fine lines. 



The Cornanche species of the genus Protocardia need careful 

 revision, and this form may be found to belong to some of the 

 numerous species already described. This species is distin- 

 guished only by a smaller size than that of all the other forms 

 described. It occurs sparsely in the beds near Glen Rose. 



