MARINE JURASSIC ROCKS IN SOUTHWESTERN TEXAS 817 
5) 110 feet coarse gypsum, same as N. 
6) 450 feet heavily bedded limestone, with many seams of calcite which 
in places are several feet wide. That is, there are places several feet wide 
where there is more calcite than limestone. Dip hard to get, but at one 
place halfway across the bed it was 75° N. 40° E.; labeled Q. 
General direction of hills nearly E. and W. The water has worn out a 
little draw in the gypsum beds between the limestone. 
Several hundred yards west of where this section was made, at the extreme 
N. W. end of these hills, near the R. R., is an outcrop of soft sandstone. 
Parties have opened this up in one or two places, in search of fossils perhaps, 
but I could find no trace of any. 
About a mile east of where I made this section, between the last two hills 
of this series, R. R. Goodell found an outcrop carrying fossils; a large clam, 
a Trigonia with rough nodular ridges, and two other bivalves. Outcrop 500 
feet long, 150 feet wide; strike N. and S.; dip about 20°E. 
Instead of four species of bivalves, however, the collection 
which the Messrs. Goodell brought back from this locality 
included seven, besides a fragment of an eighth and one of an 
ammonite. The bivalves included Pholadomya tosta (which the 
Goodell collection showed had been erroneously referred to the 
genus, Anatina); Trigonta vyschetzki; the new Trigonia of the 
Jurassic section Undulate, T. goodellit; a subcircular, strongly 
compressed shell which is either a Cyprimeria or a Lucina, and 
to which I have given the MS. specific name metrica, from its 
being ornamented with concentric, sharply raised lines disposed 
at ample and remarkably regular intervals; a plain or gently 
and irregularly concentric-undulate, elongate Plewromya—P. 
malonensis of my MS.,' showing in several examples the over- 
lapping of the left hinge-margin by the right, characteristic of 
this genus; the Venus malonensis; an indeterminate ostreid 
(shown only in section, imbedded) ; and a fragment of another 
shell, possibly a 7rigonta of the section, Costate. The Pleuromya 
bears more or less resemblance to P. henselt Hill, a Glen Rose 
species which the writer has collected at a number of localities 
«Since this and the preceding species were studied, drawn, and named, I have 
recovered a mislaid copy of Castillo and Aguilera’s ‘‘Fuana Fosil de la Sierra de 
Catorce ” (Boletin de la Comision Geologica de Mexico, Num. 1), and it seems to me 
that there can be little doubt of their belonging respectively to the Plewromya inconstans 
and Lzcina potosina of those authors. 
