Art. IX,] Herrick-Johnson, Geology of the Alhuquerqiie Sheet. 203 
Ostrea glahra, White. 
Plate XXXIV, Figs, i, 2. 
Numerous well-preserved specimens of this Laramie species 
were found east of the Caballo mountains in connection with 
the coal beds and what seems to be a somewhat different form 
of the same species occurs at Cerrillos but the association was 
not sufficiently close to determine the age of the beds of coal. 
Ostrea transhicida, Meek and Hayden. 
Plate XXXIV, Figs. 7, 8, 9 and 10. 
Ostrea pellucida. Meek and Hayden. 
Ostrea pellucida, White. 
Not Ostrea pellucida, Defrance. 
A very thin-shelled Ostrea is represented by numerous 
specimens which are probably from the “ gasteropod zone” be- 
neath the Tres Hermanos or large concretionary sandstone in 
the Rio Puerco valley. Our figures are from casts of the in- 
terior. It may prove that they indicate a new species. It would 
appear that the shell/rom Carthage figured on Plate XXXIII, 
Fig. 7 is of the same species. The plications are sometimes 
obsolescent but the general form is fairly constant. 
OsU^ea fraitklini, Coquand ? 
Plate XXIX, Fig. 8. 
Two casts of the interior from the sandstone of the mono- 
cline east of Island Mesa may belong to this or a similar spe- 
cies. Upper Fox Hills group. 
Exogyi'a laevisciila, Roemer. 
This species occurs very abundantly beneath the Tres Her- 
manos or large concretionary sandstone in the Rio Puerco val- 
ley and at Gallup with E. columbella. 
Exogyra columbellay Meek. 
Not uncommon in the “ gasteropod zone ” below the Tres 
Hermanos sandstone in the Rio Puerco valley and at Gallup. 
