Defjcrlptloitx of Sj^cclcs. 20 



idiv, with the exception of Dieenis, a Jurassic fonii, and is aljun- 

 dant in the Neocomian formation of .Spain, France, and rortugal. 



Monopleuia marcida ami M. pinguiscula White. 



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



Casts and moulds of Moiiopleura 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 al:)undant in the Ca])rina limestone, have not been found in 

 the Glen Rose beds, l)ut there is a general resendjlance of the 

 larger valves to the two species named. 



The genus Monnjikurn^ 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. 

 Jn America the genus culminates in the Ca])rina limestone and 

 is not known later. 



Coibicula arkansaensis Hill. 



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

 loo, plate ii, fig. 20; plate iv, figs. 3, 3rt, 6. 



This spedies was originally figureil and descrilied in my Ar- 

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

 freesl)oro, and at the gypsum bluffs of the Little Missouri. It is 

 less al)undant in the Texas Ijcds. 



Cardium (?) sevierense Hill. 



RArkansas (ieological Survey, Annual Report 1888, vol. ii, v». 

 134, plate ii, figs. 21, 21(/. 



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

 from which it was descril)ed in my Arkansas report. 



Protocaidia sp. indet. 



Small casts, tlirce-quarters of an inch in length, globose; sur- 

 face marking, very fine lines. 



The Comanche species of the genus Prolocardia need careful 

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

 numerous si)ecies already described. .This si)ecies 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. 



