Art. IX.] Herrick-Johnson, Geology of the Albuquevque Sheet. 207 
with the form of Trigonarca depressa. There are two varieties, 
one being shorter (figures 4 and 5) and the other more oblique. 
None of these agrees in form with the species of Idonearca fig- 
ured by Meek and Hayden though the hinge structure agrees. 
The figure by Stanton for the hinge of T. obliqua does not 
apply to our forms though the casts are apparently identical 
with those figured by him on Plate XX, Figs. 5 and 5. There 
is abundant material from the horizon above the lignite beds in 
various parts of the territory but we are unable to decide that 
that there is more than one species. 
Cardiwn pauperculufyiy Meek. ' 
Plate XXXIII, Fig. ii. 
What appears to be the species cited is abundant above the 
coal horizon at Carthage and in the Upper Fox Hills layers east 
of the Sandia mountains. We have also found it in the walls 
of the depression surrounding the Zuni salt lake in western 
Socorro county. The figure illustrates a specimen in which the 
posterior slope is unusually angulate. Considerable variation 
occurs but the costae are simple and nearly uniform in all cases. 
Cardiuniy sp. ?. 
Plate XXXV, Fig. i. 
This fine large species we have so far failed to identify but 
not having access to all the descriptions we are unable to state 
whether it is new or not. It is not rare in the upper Fox Hills 
layers east of San Francisco in the Rio Puerco valley. 
Pholadomya suhventncosa^ Meek and Hayden. 
Plate XXX, Figs, i and 2. 
Several specimens of this species were found in the sep- 
taria concretion of the cephalopod shales near San Francisco in 
the Rio Puerco valley. 
Pinna petrina^ White. 
Plate XXXI, Fig. 5. 
A large series of this striking species found near the orig- 
inal locality in the Rio Puerco valley and elsewhere in Bernalillo 
