GEOLOGY OF NORTH AMERICA 
33 
of the Canton of Zurich, and in the Upper Sands of Montpellier. Its slratigraphical position in Eu- 
rope is in the Miocene epoch. It is probable that the strata of Carrizo creek belong to the Mio- 
cene or perhaps the Pliocene epoch. 
E(cplatialion of figures. - Pl.ite V, fig. 2. Lower valve, broken; front view. 
» fig. 2 a. The same, side view. 
FOSSILS OF THE CRETACEOUS ROCKS. 
PTYf.nODCS WHIPPLEI n. sp. 
Plate I, fig. f. -i a. 
Description. — Tooth having the form of an obtuse rather square cone; the great folds of enamel are confined 
to the apex of the tooth , and are quite worn away on the specimen figured ; the hody of the tooth is finely gra- 
nulated; its height is considerable, and the edges of the base are ornamented with small irregular folds. 
Observations. — The great folds of enamel being worn away, probably in eating, would lead one 
to doubt that this tooth is a true Plychodus; but Prof. Agassiz examined this specimen and recognized it 
at once as a new species of his genus Plychodus. It resembles very much the Ptychodus allior .Agass. 
(See: Poissons FossUes; vol. Ill, page 155; and especially The Geology and Fossils of Sussex, bv Fred. 
Dixon, page 362. tab. XXX, fig. 10.) of the White Chalk of Europe. 
Locality. — Is found in the gray sandy marls three miles north of Galisteo, on the road from 
Galisteo to Pecos , New Mexico. I found in company with this Ptychodus a septa of a larg-e Am- 
monite , too badly preserved to admit of a specific determination ; numerous fragments of a large 
Inoeeramus, probably the Inoceramus Cripsii Mant. (see: Die Kreidebildungen von Texas, by Roemer, 
pag. 56, tab. VII, fig. 2,); and also a small sinuous Ostrea, with a very thin shell, that Meek and 
Hayden (See: Proceedings Acad. Nat. Sc.; Philadelphia.) identify with Ostrea congesta. These gray 
sandy marls of Galisteo represent the upper part of the Cretaceous rocks of the United States, and 
are probably equivalent to the White Chalk. They rest, in discordant stratification, upon the yellow 
sandstone strata of the Jurassic epoch. It must be remembered that these gray sandy marls have 
nothing to do with the Jurassic Blue Clay containing Gryphaia dilatata var. Tucumcarii of the Llano 
Estacado ; they are much younger. 
I dedicate this beautiful species of cretaceous fish to my friend Capt. A. W. Whipple, the able 
and learned chief of our Exploration in the Rocky Mountains. 
KxptanaUon of figures. — Plaie I, fig. 4. Tooth of natural size, side vioxv. 
« I, fig. 4 a. The same, front view. 
AMMONITES SHUMARDI n. sp. 
Plate I , fig. 1. la. 
Desenplion. — Shell inflated , large , carinated , each whorl ornamented near the umbilicus with 20 prominent 
tubercles, which must have been armed with points, and are placed at the angle of the whorl. Each tubercle ge- 
nerally gives rise to two large rounded ribs that terminate at the keel in bending slightly toward the mouth. Each 
rib is ornamented with a tubercle, placed at the angle of the whorl near the back, less prominent than those near 
the umbilicus. Breadth of whorls equal to height, form subquadrangular , larger toward the umbilicus than at the 
tubercles forming the angle near the back. Back convex, large, with a sharp keel. Lateral septa trilobated. 
Observations. — This species differs from all the Cretaceous Ammonites hitherto described ; it re- 
sembles slightly the Am. coronatus of the Oxfordian, but is distinguished by its two lines of tubcrclo.s 
and its keeled back. It is one of the largest species found as yet in America. 
