44 
GEOLOGY 
Observations. — I find no difference between the two specimens collected at Pyramid Mount, and 
more than fifty of the true Oslrea Marshii Sow. [The Mineral Conchology of Great Britain, table XLVIll.) 
found by me in the Lower Oolite of the Jura mountains. It resembles the Ostrea pes-leonis Vorhes , of 
Pondicherry. East India (See: Report on the fossil invertebrata from Southern India, pi. 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 Gryphcea di- 
latata var. Tucumcarii at Pyramid Mount. It is much more rare than the Gryphcea, 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. 
Kxplanation of figure. — Plate IV , fig. 4. Valve natural size , front view of the exterior. 
FOSSILS OF THE MOUNTAIN LIMESTONE 
OR 
LOWER CARBONIFEROUS ROCKS. 
ORTHOCER.4S iNOVA-MEXICAN.A n. sp. 
Plate VII, fig. 1. 
Description. — Shell elongate, cylindrical, smooth, section circular; the siphuncle is not visible on my speci- 
men , 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 Ilellerophon be- 
cause I have found no other in the Rocky mountains, and it is probable they are numerous there hut that I failed 
to find the bed in which they lay. 
Observations. — This species is related to the Orthoceras giganteum Sow. (See : Min. Conch, of Great 
Britain, tab. 246; and Fossiles du Carbonifere 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 sum- 
mit of the Sierra de Sandia, behind Albuquerque. 
Explanalim of figure. — Plate VII, fig. 1. Natural size, side view. 
AIYALINA APACHESI n. sp. 
Plate VII, 6,6 a. 
Description. — ■ Shell oblique-elongated , depressed , thick ; concentric strite ; 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; pi. 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; pi. 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; 1 have seen only 
three specimens and not one is perfect. 
