44
Observations. — I find no difference between the two specimens collected at Pyramid Mount, and more than fifty of the true Ostrea Marshii Sow. (The Mineral Conchology of Great Britain, table XLVIII.) found by me in the Lower Oolite of the Jura mountains. It resembles the Ostrea pes-leonis Forbes, of Pondicherry, East India (See : Report on the fossil invertebrata from Southern India, pl. XVIII, fig. 5.); but the furrows towards the margin are less deep, the plications less acutely angular, and the shell is not ovate but oblique.
Locality. — 1 found this fine Jurassic species in the same bed a of clay with the Gryphæa dilatata var. Tucumcarii at Pyramid Mount. It is much more rare than the Gryphæa, for I only found two specimens, but it is probable, that a longer and more minute search in the vicinity of Plaza Larga would result in the discovery of a more considerable number.
Explanation of figure. —
- Plate IV, fig. 4. Valve natural size , front view of the exterior.
FOSSILS OF THE MOUNTAIN LIMESTONE
OR
LOWER
CARBONIFEROUS ROCKS.
ORTHOCERAS NOVA-MEXICANA n. sp.
Plate VII , fig. 1.
Description. — Shell elongate, cylindrical , smooth, section circular; the siphuncle is not visible on my specimen , which has only the two last chambers; if we can judge from the last chamber but one, they must have been numerous, regularly concave and succeeding each other at small distances. The last chamber is large, its length being twice its diameter. In this last chamber is seen the section of a Bellerophon. I notice this Bellerophon because I have found no other in the Rocky mountains, and it is probable they are numerons there but that I failed to find the bed in which they lay.
Observations. — This species is related to the Orthoceras giganteun Sow. (See : Min. Conch. of Great Britain, tab. 246; and Fossiles du Carbonifère de Belgique, par de Koninck; p. 510, tab. 44, 45, 46 and 47.), but it is more cylindrical and the chambers appear much nearer together.
Locality. — I found only one specimen of this species; it was in a block of blue limestone, with several beautiful specimens of the Productus semi-reticulatus, in a deep ravine near the summit of the Sierra de Sandia, behind Albuquerque.
Explanation of figure.—
- Plate VII, fig. 1. Natural size, side view.
Description. — Shell oblique-elongated , depressed, thick ; concentric stria ; beak pointed with small crochet slightly bent , the cardinal border is not visible in my specimens , the three other borders are more or less round.
Observations. — This fossil resembles very much the Myalina virgula of de Koninck (See : Descr. des Foss. Carbonif. de Belgique, p. 127; pl. VI, fig. 3.), but it is larger and its form is more elongated and not sub-rhomboidal. It is entirely distinct from the only species of Myalina hitherto discovered in the United States, and described under the name of Myalina sub-quadrata Shumard (See: First Report of the Geol. Survey of Missouri; second part, p. 207; pl. c, fig. 17 a , 17 b; found in the Coal Measures of the Missouri river.).
Locality. — It is found in company with the Productus semi-reticulatus, the Spirifer striatus, and the Terebratula subtilita, near the ranchos of Pecos village. This species is rare ; I have seen only three specimens and not one is perfect.