42 
GEOLOGY 
(Ired specimens from the following localities: Cross Timbers, Fort Arbuckle; Headwaters of the Rio Co- 
lorado, Texas; and the vicinity of Fredericksburg and New Braunfelds. This species varies very much, 
and I agree with Dr. B. F. Shumard who says: «They [Ex. Texana) vary very much in their characters, 
« scarcely any two examples being alike. In some the shell is quite thin , in others massive ; some ex- 
« hibit prominent rugose ribs, while in others the ribs are but slightly elevated and nodulose » (See; Pa- 
leontology, in the Exploration of the Red river of Louisiana, in the year 1852, by Capt. R. B. Marcy; 
pag. 205.). Roomer, though he remarks the great similarity of this species to the Ostrea BoussingauUii 
d’Orb. and Exogyra Overwegi L. de Buch, and even goes so far as to identify it in part with certain 
lorms of the Ostrea Matheroniana d’Orb., persists nevertheless in considering it a distinct species. After 
an attentive comparison, I see no reason for such a conclusion, and I regard it as identical with the 
Ex. flahellata Goldfuss [Petrif. Germ., tome II, pag. 38; pi. 87, fig. 6 a.) and the Exogyra BoussingauUii 
d’Orbigny (Pafe'ont. Frang., Ter. Grit., tome III, pag. 702, pi. 468; and Coquilles Fossiles de la Nouvelle 
Grenade recueillis par Boussingault , pag. 57, pi. Ill, fig. 20; and pi. V, fig. 8, 9.). So that the Ex. fla- 
bellata is one of the Cretaceous fossils having the widest geographical extension, being found in France; 
England; Germany; Spain; Mount Lebanon, Asia; Texas, North America; New Grenada and Venezuela, 
South America. In consequence of the vast extent of surface occupied by this fossil, I consider it as 
forming a family of which the Exogyra plicata Goldf. (Petrif. Germ., tome II, pag. 37, pi. 87, fig. 5 a f.) 
is a variety having the umbonos nearer the edge, and the general form more elongated and carinated. 
The Ostrea Matheroniana d’Orb. (PaUont. Frang., Ter. Crdt., tome III, pag. 737, pi. 485.) is another va- 
riety of it, narrower and more carinated; and finally the Exogyra Overwegi Leopold de Buch (Bericht 
iiber die von Overweg auf der Reise von Tripoli nach Murzuk, und von Murzuk nach Ghat gefundenen Yerstei- 
nerungen , by Herr Beyrich, pag. 161 of Berliner Monatsberichte , neuo Folge, tome 9, tab. I, fig. 1 a, 
I b, 1 c.) is a third variety of the Ex. jlabellata-, it is more convex and the beak is more enrolled and 
more distant from the cardinal edge. Beyrich takes the Ex. plicata Goldf. as type of a family, and com- 
pares with it the Exogyra; of Overweg, of Matheron , of Boussingault and the Texan. On the contrary, 
d’Orbigny in his PaUontologie Frangaise considers the Ex. plicata Goldfuss as identical with the Ex. fla- 
bellata, and he unites them by the name of Ex. jlabellata. Further he says, vol. 3, page 703, that 
the Ex. BoussingauUii resembles so closely the Ex. jlabellata, that he can not distinguish the specimens 
from each other, and that he would not hesitate to unite them, if they had been found in the same strata-, 
thus sacrificing the zoological characters to a preconceived and false idea of the complete extinction of 
all the species in each division of the Earth’s strata. 
CYTIIEREA MISSOURIANA Mort. and TELLINA OCCIDENTALIS Mort. 
Description. — See : Description oj some new species oj organic remains of the Cretaceous group of the United States : 
by S. G. Morton, in the Journal of the Academy of Natural Sciences, vol. 8, pi. XI, fig. 2 and 3. Philadelphia, 1842. 
Observations and Locality. — 1 identify with these two fossils a great number of bivalves form- 
ing a lumachella in a yellowish-gray limestone placed between the gray marls that occupy the 
country between Gold Mount and the villages of Galisteo and Algodones in New Mexico. These marls 
and limestones belong to the upper Cretaceous epoch, and are probably of the same age as the 
White Chalk. 
CAPROTLVA TEXANA Roem. 
Description. — See: Die Kreidebildungen von Texas, von F. Roemer. plate V, fig, 2 a, 2 b, 2 c; page 80. 
Observations and Locality. — I have seen several specimens of this species in the limestones 
with Grypheea Pitcheri of the hills surrounding Comet creek, on the left bank of the False Washita. 
Roemer also says that he found it in company with the G. Pitcheri in the vicinity of New' Braun- 
felds; so that this species may be considered as one of the Neocomian fossils of Texas. 
