OF NORTH AMERICA. 
35 
above the sea-level, found beds of shells containing an immense quantity of oysters and fragments of 
Ammonites, These shell fields are known in the country by the name of Choropampas. Among the fos- 
sils collected at Montan, de Humboldt brought back very large fragments, more than a foot in length 
and half a foot in width. Leopold de Buch, the great german geologist, who published the fossils of 
this exploration under the title: <iP4tri/ications recueillies en Amerique, par Alex, de Humboldt et par Charles 
Degenhardt; in folio; Berlin, 1839 », recognized these fragments as belonging to an Ammonite of the 
Cristati family; although they presented certain characters usually proper to the Hamiles-, and he gave 
them the name of Ammonites peruvianus. Since then Dr. Hermann Karsten has found it at Barbacoes 
near Truxillo in Venezuela. 
It is rather remarkable that I have also a large fragment of nearly the same size and form with 
the one figured by de Buch under the number 5; but 1 have also a young and complete specimen of 
the same species. This complete specimen shows that de Buch was right to connect the fragments found 
by Humboldt with Ammonites and not with the Hamltes, and that with his accustomed sagacity, so well 
known to all geologists, he had rightly judged regarding them. 
My friend Dr. George G. Shumard of Fort Smith, Arkansas, has found numerous examples of the 
same species at Cross Timbers, Texas; and his brother, Dr. B. J. Shumard, described and figured it 
in the report of the Exploration of the Red river, by Capt. Marcy, under the name of Am. acuto-carinatns 
(See: Paleontology of the Expedition of the Red river of Louisiana, page 209, plate HI, fig. 1.). It cannot 
be recognized by the figure, it is so badly drawn, but the description of Shumard is so exactly appli- 
cable to my specimens, that I have no doubt they are the same species. 
Locality. — In the Cretaceous strata forming: the bed of Elm Fork river , an atlliient of Tri- 
nity river, Texas. 
Explanation of figures. — Plate V, fig. 1 . Side view of a large fragment. 
» V, fig. t a. Young individual, side view. 
» V , fig. 1 b. The same , front view. 
-AMMONITES GIBHONIANUS Lea. 
Plate It , fig. 2a, 2 b. 
Description. — The only fragment I possess shows that this Ammonite must be of large size. The whorls are 
compressed , not much overlapped ; ribs simple , elevated , carinated . not crossing the back , slightly flexuous at the 
umbilicus, large and somewhat distant at the periphery; back probably sharply carinated, section of the whorls 
elongate-cordate; septa narrow, with lobes quite numerous and ramified. 
Observations. — This species appears to be identical with that figured and described by my friend 
Isaac Lea in vol. VII of the Philosophical Transactions, Philadelphia, called by him .4m. Gibbonianus {See: 
Notice of the Oolitic Formation in America, with descriptions of some of its organic remains- plate VlII 
fig. 3. 1840.). 
It is singular that the fragment in my possession is hardly larger than that of Lea , mine having 
eleven ribs while his has only six; but mine is better preserved and shows a little of the keel. Lea’s 
specimen was found in the Cretaceous rocks between Tocaima and La Messa. New Grenada, by Dr. Gibbon. 
Locality. — My specimen was found in the Cretaceous limestone forming^ the bed of the Elm 
Fork, one of the affluents of Trinity river, Texas. 
Explanation of figures. — Plate II , fig. 2 a. Side view. 
I) 'll , fig. 2 b. Section of whorls , and -A B of specimen fig. 2 a. 
AMMONITES NOVI-MEXICANI n. sp. 
Plate I, fig. 2 , 2 a. 
Description. I have only two very incomplete fragments of this species. I have figured the smallest, which 
is the best preserved of the two. My principal inducement for publishing it is the large and square form of the 
